diff --git a/.env.ci b/.env.ci
index b868fd46e..f5d3c52cb 100644
--- a/.env.ci
+++ b/.env.ci
@@ -10,3 +10,4 @@ AUTHBROKER_URL=
 SENTRY_ENVIRONMENT=ci
 SENTRY_DSN=
 CSP_REPORT_URI=
+PAYROLL={"BASIC_PAY_NAC": "71111001", "PENSION_NAC": "71111002", "ERNIC_NAC": "71111003", "VACANCY_NAC": "71111001"}
diff --git a/.env.example b/.env.example
index d0afcc561..3d8059296 100644
--- a/.env.example
+++ b/.env.example
@@ -32,6 +32,8 @@ CSP_REPORT_URI=
 # Vite
 VITE_DEV=True
 
+PAYROLL={"BASIC_PAY_NAC": "71111001", "PENSION_NAC": "71111002", "ERNIC_NAC": "71111003", "VACANCY_NAC": "71111001"}
+
 # Not documented (needed?)
 # RESTRICT_ADMIN=True
 # PUBLIC_PATH="http://localhost:8000"
diff --git a/config/settings/base.py b/config/settings/base.py
index 9ee479b67..2d3c4c5c5 100644
--- a/config/settings/base.py
+++ b/config/settings/base.py
@@ -11,6 +11,7 @@
 """
 
 import os
+from dataclasses import dataclass
 from pathlib import Path
 
 import dj_database_url
@@ -415,3 +416,16 @@ def FILTERS_VERBOSE_LOOKUPS():
 
 CSP_REPORT_ONLY = True
 CSP_REPORT_URI = env.str("CSP_REPORT_URI", default=None)
+
+
+# Payroll
+@dataclass
+class Payroll:
+    BASIC_PAY_NAC: str | None = None
+    PENSION_NAC: str | None = None
+    ERNIC_NAC: str | None = None
+    VACANCY_NAC: str | None = None
+    AVERAGE_SALARY_THRESHOLD: int = 2
+
+
+PAYROLL: Payroll = Payroll(**env.json("PAYROLL", default={}))
diff --git a/core/constants.py b/core/constants.py
new file mode 100644
index 000000000..b580d3824
--- /dev/null
+++ b/core/constants.py
@@ -0,0 +1,17 @@
+from .types import Months
+
+
+MONTHS: Months = (
+    "apr",
+    "may",
+    "jun",
+    "jul",
+    "aug",
+    "sep",
+    "oct",
+    "nov",
+    "dec",
+    "jan",
+    "feb",
+    "mar",
+)
diff --git a/core/types.py b/core/types.py
new file mode 100644
index 000000000..3e7427ef2
--- /dev/null
+++ b/core/types.py
@@ -0,0 +1,46 @@
+from typing import Literal, TypedDict
+
+
+Month = Literal[
+    "apr",
+    "may",
+    "jun",
+    "jul",
+    "aug",
+    "sep",
+    "oct",
+    "nov",
+    "dec",
+    "jan",
+    "feb",
+    "mar",
+]
+Months = tuple[
+    Literal["apr"],
+    Literal["may"],
+    Literal["jun"],
+    Literal["jul"],
+    Literal["aug"],
+    Literal["sep"],
+    Literal["oct"],
+    Literal["nov"],
+    Literal["dec"],
+    Literal["jan"],
+    Literal["feb"],
+    Literal["mar"],
+]
+
+
+class MonthsDict[T](TypedDict):
+    apr: T
+    may: T
+    jun: T
+    jul: T
+    aug: T
+    sep: T
+    oct: T
+    nov: T
+    dec: T
+    jan: T
+    feb: T
+    mar: T
diff --git a/core/urls.py b/core/urls.py
index 50babc924..8c5a6febf 100644
--- a/core/urls.py
+++ b/core/urls.py
@@ -7,5 +7,5 @@
     path("", views.index, name="index"),
     path("logout", views.logout, name="logout"),
     path("accessibility", views.AccessibilityPageView.as_view(), name="accessibility"),
-    path("report/budget-report", views.budget_report, name="report:budget_report"),
+    path("report/budget-report", views.budget_report, name="budget-report"),
 ]
diff --git a/forecast/templatetags/forecast_format.py b/forecast/templatetags/forecast_format.py
index 42a84a0fc..8b01103b8 100644
--- a/forecast/templatetags/forecast_format.py
+++ b/forecast/templatetags/forecast_format.py
@@ -37,6 +37,19 @@
 ]
 
 
+@register.filter
+def format_money(value: float) -> str:
+    """Format as a monetary value.
+
+    `value` is expected to be in pence and will be divided by 100.
+
+    Examples:
+        >>> format_money(1024312)
+        '10,243.12'
+    """
+    return f"{value / 100:,.2f}"
+
+
 @register.filter()
 def is_forecast_figure(_, column):
     if str(column) in forecast_figure_cols:
diff --git a/front_end/src/Util.js b/front_end/src/Util.js
index 7aeb4deda..5f20d070f 100644
--- a/front_end/src/Util.js
+++ b/front_end/src/Util.js
@@ -168,10 +168,8 @@ export const processForecastData = (forecastData, payrollData = null, isPayrollE
           let overrideAmount = null
 
           if (isPayrollEnabled && mappedPayrollData[forecastKey]) {
-            const period = `period_${(parseInt(key)+1)}_sum`
-            // TODO (FFT-99): Decide on decimal vs pence
-            // Old code stores monetary values in pence whereas new code has used decimals.
-            overrideAmount = mappedPayrollData[forecastKey][period] * 100
+            const period = months[parseInt(key)]
+            overrideAmount = mappedPayrollData[forecastKey][period]
           }
 
             cells[monthlyFigure.month] = {
@@ -197,8 +195,8 @@ const processPayrollData = (payrollData) => {
   const results = {};
 
   for (const [key, value] of Object.entries(payrollData)) {
-    const generatedKey = makeFinancialCodeKey(value.programme_code, value.pay_element__type__group__natural_code)
-    
+    const generatedKey = makeFinancialCodeKey(value.programme_code, value.natural_account_code)
+
     results[generatedKey] = value;
   }
 
diff --git a/payroll/fixtures/test_payroll_data.json b/payroll/fixtures/test_payroll_data.json
index 3c75997cb..ad5af4fb5 100644
--- a/payroll/fixtures/test_payroll_data.json
+++ b/payroll/fixtures/test_payroll_data.json
@@ -9,7 +9,10 @@
       "first_name": "John",
       "last_name": "Smith",
       "grade": "Grade 7",
-      "assignment_status": "Active Assignment"
+      "assignment_status": "Active Assignment",
+      "basic_pay": 230000,
+      "pension": 40000,
+      "ernic": 9000
     }
   },
   {
@@ -22,7 +25,10 @@
       "first_name": "Jane",
       "last_name": "Doe",
       "grade": "Grade 7",
-      "assignment_status": "Active Contingent Assignment"
+      "assignment_status": "Active Contingent Assignment",
+      "basic_pay": 268000,
+      "pension": 60000,
+      "ernic": 50000
     }
   },
   {
@@ -35,7 +41,10 @@
       "first_name": "John",
       "last_name": "Doe",
       "grade": "Grade 7",
-      "assignment_status": "Loan Out - Non Payroll"
+      "assignment_status": "Loan Out - Non Payroll",
+      "basic_pay": 0,
+      "pension": 0,
+      "ernic": 0
     }
   },
   {
@@ -48,7 +57,10 @@
       "first_name": "Jane",
       "last_name": "Smith",
       "grade": "Grade 7",
-      "assignment_status": "Active Assignment"
+      "assignment_status": "Active Assignment",
+      "basic_pay": 0,
+      "pension": 0,
+      "ernic": 0
     }
   },
   {
diff --git a/payroll/migrations/0015_employee_basic_pay_employee_ernic_employee_pension.py b/payroll/migrations/0015_employee_basic_pay_employee_ernic_employee_pension.py
new file mode 100644
index 000000000..59f056722
--- /dev/null
+++ b/payroll/migrations/0015_employee_basic_pay_employee_ernic_employee_pension.py
@@ -0,0 +1,28 @@
+# Generated by Django 4.2.16 on 2024-11-27 14:59
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("payroll", "0014_alter_vacancypayperiods_vacancy"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="employee",
+            name="basic_pay",
+            field=models.BigIntegerField(db_comment="pence", default=0),
+        ),
+        migrations.AddField(
+            model_name="employee",
+            name="ernic",
+            field=models.BigIntegerField(db_comment="pence", default=0),
+        ),
+        migrations.AddField(
+            model_name="employee",
+            name="pension",
+            field=models.BigIntegerField(db_comment="pence", default=0),
+        ),
+    ]
diff --git a/payroll/models.py b/payroll/models.py
index 0bba5a49f..237012aa1 100644
--- a/payroll/models.py
+++ b/payroll/models.py
@@ -17,6 +17,9 @@ def with_basic_pay(self):
             )
         )
 
+    def payroll(self):
+        return self.filter(basic_pay__gt=0)
+
 
 class Position(models.Model):
     class Meta:
@@ -87,6 +90,9 @@ class Employee(Position):
     first_name = models.CharField(max_length=32)
     last_name = models.CharField(max_length=32)
     assignment_status = models.CharField(max_length=32)
+    basic_pay = models.BigIntegerField(default=0, db_comment="pence")
+    pension = models.BigIntegerField(default=0, db_comment="pence")
+    ernic = models.BigIntegerField(default=0, db_comment="pence")
 
     # TODO: Missing fields from Admin Tool which aren't required yet.
     # EU/Non-EU (from programme code model)
@@ -148,44 +154,46 @@ class EmployeePayElement(models.Model):
     credit_amount = models.DecimalField(max_digits=9, decimal_places=2)
 
 
-class RecruitmentType(models.TextChoices):
-    EXPRESSION_OF_INTEREST = "expression_of_interest", "Expression of Interest"
-    EXTERNAL_RECRUITMENT_NON_BULK = (
-        "external_recruitment_non_bulk",
-        "External Recruitment (Non Bulk)",
-    )
-    EXTERNAL_RECRUITMENT_BULK = (
-        "external_recruitment_bulk",
-        "External Recruitment (Bulk campaign)",
-    )
-    INTERNAL_MANAGED_MOVE = "internal_managed_move", "Internal Managed Move"
-    INTERNAL_REDEPLOYMENT = "internal_redeployment", "Internal Redeployment"
-    OTHER = "other", "Other"
-    INACTIVE_POST = "inactive_post", "Inactive Post"
-    EXPECTED_UNKNOWN_LEAVERS = "expected_unknown_leavers", "Expected Unknown Leavers"
-    MISSING_STAFF = "missing_staff", "Missing Staff"
-
-
-class RecruitmentStage(models.IntegerChoices):
-    PREPARING = 1, "Preparing"
-    ADVERT = 2, "Advert (Vac ref to be provided)"
-    SIFT = 3, "Sift"
-    INTERVIEW = 4, "Interview"
-    ONBOARDING = 5, "Onboarding"
-    UNSUCCESSFUL_RECRUITMENT = 6, "Unsuccessful recruitment"
-    NOT_YET_ADVERTISED = 7, "Not (yet) advertised"
-    NOT_REQUIRED = 8, "Not required"
-
-
 class Vacancy(Position):
     class Meta:
         verbose_name_plural = "Vacancies"
 
+    class RecruitmentType(models.TextChoices):
+        EXPRESSION_OF_INTEREST = "expression_of_interest", "Expression of Interest"
+        EXTERNAL_RECRUITMENT_NON_BULK = (
+            "external_recruitment_non_bulk",
+            "External Recruitment (Non Bulk)",
+        )
+        EXTERNAL_RECRUITMENT_BULK = (
+            "external_recruitment_bulk",
+            "External Recruitment (Bulk campaign)",
+        )
+        INTERNAL_MANAGED_MOVE = "internal_managed_move", "Internal Managed Move"
+        INTERNAL_REDEPLOYMENT = "internal_redeployment", "Internal Redeployment"
+        OTHER = "other", "Other"
+        INACTIVE_POST = "inactive_post", "Inactive Post"
+        EXPECTED_UNKNOWN_LEAVERS = (
+            "expected_unknown_leavers",
+            "Expected Unknown Leavers",
+        )
+        MISSING_STAFF = "missing_staff", "Missing Staff"
+
     recruitment_type = models.CharField(
         max_length=29,
         choices=RecruitmentType.choices,
         default=RecruitmentType.EXPRESSION_OF_INTEREST,
     )
+
+    class RecruitmentStage(models.IntegerChoices):
+        PREPARING = 1, "Preparing"
+        ADVERT = 2, "Advert (Vac ref to be provided)"
+        SIFT = 3, "Sift"
+        INTERVIEW = 4, "Interview"
+        ONBOARDING = 5, "Onboarding"
+        UNSUCCESSFUL_RECRUITMENT = 6, "Unsuccessful recruitment"
+        NOT_YET_ADVERTISED = 7, "Not (yet) advertised"
+        NOT_REQUIRED = 8, "Not required"
+
     recruitment_stage = models.IntegerField(
         choices=RecruitmentStage.choices, default=RecruitmentStage.PREPARING
     )
diff --git a/payroll/services/payroll.py b/payroll/services/payroll.py
index 8592da33d..b0418f15d 100644
--- a/payroll/services/payroll.py
+++ b/payroll/services/payroll.py
@@ -1,11 +1,18 @@
-from decimal import Decimal
+from collections import defaultdict
+from statistics import mean
 from typing import Iterator, TypedDict
 
+import numpy as np
+import numpy.typing as npt
+from django.conf import settings
 from django.db import transaction
-from django.db.models import F, Q, Sum
+from django.db.models import Avg, Count, Q
 
+from core.constants import MONTHS
 from core.models import FinancialYear
+from core.types import MonthsDict
 from costcentre.models import CostCentre
+from gifthospitality.models import Grade
 
 from ..models import Employee, EmployeePayPeriods, Vacancy, VacancyPayPeriods
 
@@ -51,36 +58,89 @@ def create_pay_periods(instance, pay_period_enabled=None) -> None:
         )
 
 
-def payroll_forecast_report(cost_centre: CostCentre, financial_year: FinancialYear):
-    period_sum_annotations = {
-        f"period_{i+1}_sum": Sum(
-            F("pay_element__debit_amount") - F("pay_element__credit_amount"),
-            filter=Q(**{f"pay_periods__period_{i+1}": True}),
-            default=Decimal(0),
-        )
-        for i in range(12)
-    }
+class PayrollForecast(MonthsDict[float]):
+    programme_code: str
+    natural_account_code: str
 
-    qs = (
-        Employee.objects.filter(
-            cost_centre=cost_centre,
-            pay_periods__year=financial_year,
-            pay_element__isnull=False,
-        )
-        .order_by(
-            "programme_code",
-            "pay_element__type__group",
-        )
-        .values(
-            "programme_code",
-            "pay_element__type__group__natural_code",
-            "pay_element__type__group",
-            "pay_element__type__group__name",
-        )
-        .annotate(**period_sum_annotations)
+
+def payroll_forecast_report(
+    cost_centre: CostCentre, financial_year: FinancialYear
+) -> Iterator[PayrollForecast]:
+    # { programme_code: { natural_account_code: np.array[ np.float64 ] } }
+    report: dict[str, dict[str, npt.NDArray[np.float64]]] = defaultdict(
+        lambda: defaultdict(lambda: np.zeros(12))
+    )
+
+    employee_qs = Employee.objects.filter(
+        cost_centre=cost_centre,
+        pay_periods__year=financial_year,
     )
+    for employee in employee_qs.iterator():
+        periods = employee.pay_periods.first().periods
+        periods = np.array(periods)
+
+        prog_report = report[employee.programme_code_id]
+        prog_report[settings.PAYROLL.BASIC_PAY_NAC] += periods * employee.basic_pay
+        prog_report[settings.PAYROLL.PENSION_NAC] += periods * employee.pension
+        prog_report[settings.PAYROLL.ERNIC_NAC] += periods * employee.ernic
+
+    vacancy_qs = Vacancy.objects.filter(
+        cost_centre=cost_centre,
+        pay_periods__year=financial_year,
+    )
+    for vacancy in vacancy_qs.iterator():
+        avg_salary = get_average_salary_for_grade(vacancy.grade, cost_centre)
+        salary = vacancy.fte * avg_salary
+
+        periods = vacancy.pay_periods.first().periods
+        periods = np.array(periods)
+
+        prog_report = report[vacancy.programme_code_id]
+        prog_report[settings.PAYROLL.VACANCY_NAC] += periods * salary
 
-    return qs
+    for programme_code in report:
+        for nac, forecast in report[programme_code].items():
+            forecast_months: MonthsDict[float] = dict(zip(MONTHS, forecast, strict=False))  # type: ignore
+
+            yield PayrollForecast(
+                programme_code=programme_code,
+                natural_account_code=nac,
+                **forecast_months,
+            )
+
+
+# TODO (FFT-131): Apply caching to the average salary calculation
+def get_average_salary_for_grade(grade: Grade, cost_centre: CostCentre) -> int:
+    employee_count_threshold = settings.PAYROLL.AVERAGE_SALARY_THRESHOLD
+
+    # Expanding scope filters which start at the cost centre and end at all employees.
+    filters = [
+        Q(cost_centre=cost_centre),
+        Q(cost_centre__directorate=cost_centre.directorate),
+        Q(cost_centre__directorate__group=cost_centre.directorate.group),
+        Q(),
+    ]
+
+    salaries: list[int] = []
+
+    for filter in filters:
+        employee_qs = Employee.objects.payroll().filter(grade=grade).filter(filter)
+
+        basic_pay = employee_qs.aggregate(
+            count=Count("basic_pay"), avg=Avg("basic_pay")
+        )
+
+        if basic_pay["count"] >= employee_count_threshold:
+            return basic_pay["avg"]
+
+        if basic_pay["count"]:
+            salaries += list(employee_qs.values_list("basic_pay", flat=True))
+
+    if salaries:
+        return round(mean(salaries))  # pence
+
+    # TODO: What do we do if there were no employees at all found at that grade?
+    return 0
 
 
 class EmployeePayroll(TypedDict):
@@ -111,7 +171,6 @@ def get_payroll_data(
             cost_centre=cost_centre,
             pay_periods__year=financial_year,
         )
-        .with_basic_pay()
     )
     for obj in qs:
         yield EmployeePayroll(
@@ -168,6 +227,7 @@ class Vacancies(TypedDict):
     id: int
     grade: str
     programme_code: str
+    budget_type: str
     recruitment_type: str
     recruitment_stage: str
     appointee_name: str
diff --git a/payroll/templates/payroll/page/edit_payroll.html b/payroll/templates/payroll/page/edit_payroll.html
index fcb92437d..fb4bf739c 100644
--- a/payroll/templates/payroll/page/edit_payroll.html
+++ b/payroll/templates/payroll/page/edit_payroll.html
@@ -1,5 +1,5 @@
 {% extends "base_generic.html" %}
-{% load breadcrumbs vite %}
+{% load breadcrumbs vite forecast_format %}
 
 {% block title %}Edit payroll{% endblock title %}
 
@@ -15,40 +15,39 @@ <h1 class="govuk-heading-l">Edit payroll</h1>
     <div id="payroll-app"></div>
 
     <h2 class="govuk-heading-m">Payroll forecast</h2>
+
     <div class="scrollable">
-      <table class="govuk-table">
-          <thead class="govuk-table__head">
-              <tr class="govuk-table__row">
-                  <th scope="col" class="govuk-table__header">Programme code</th>
-                  <th scope="col" class="govuk-table__header">Natural code</th>
-                  <th scope="col" class="govuk-table__header">Pay type</th>
-                  {% for month in months %}
-                      <th scope="col" class="govuk-table__header">{{ month }}</th>
-                  {% endfor %}
-              </tr>
-          </thead>
-          <tbody class="govuk-table__body">
-              {% for row in payroll_forecast_report %}
-                  <tr class="govuk-table__row">
-                      <th scope="row" class="govuk-table__header">{{ row.programme_code }}</th>
-                      <th scope="row" class="govuk-table__header">{{ row.pay_element__type__group__natural_code }}</th>
-                      <th scope="row" class="govuk-table__header">{{ row.pay_element__type__group__name }}</th>
-                      <td class="govuk-table__cell">{{ row.period_1_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_2_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_3_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_4_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_5_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_6_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_7_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_8_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_9_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_10_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_11_sum }}</td>
-                      <td class="govuk-table__cell">{{ row.period_12_sum }}</td>
-                  </tr>
-              {% endfor %}
-          </tbody>
-      </table>
+        <table class="govuk-table">
+            <thead class="govuk-table__head">
+                <tr class="govuk-table__row">
+                    <th scope="col" class="govuk-table__header">Programme code</th>
+                    <th scope="col" class="govuk-table__header">Natural account code</th>
+                    {% for month in months %}
+                        <th scope="col" class="govuk-table__header">{{ month }}</th>
+                    {% endfor %}
+                </tr>
+            </thead>
+            <tbody class="govuk-table__body">
+                {% for row in payroll_forecast_report %}
+                    <tr class="govuk-table__row">
+                        <th scope="row" class="govuk-table__header">{{ row.programme_code }}</th>
+                        <th scope="row" class="govuk-table__header">{{ row.natural_account_code }}</th>
+                        <td class="govuk-table__cell">£{{ row.apr|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.may|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.jun|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.jul|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.aug|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.sep|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.oct|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.nov|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.dec|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.jan|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.feb|format_money }}</td>
+                        <td class="govuk-table__cell">£{{ row.mar|format_money }}</td>
+                    </tr>
+                {% endfor %}
+            </tbody>
+        </table>
     </div>
 {% endblock content %}
 
diff --git a/payroll/tests/factories.py b/payroll/tests/factories.py
index ed2f5534a..0cba8b153 100644
--- a/payroll/tests/factories.py
+++ b/payroll/tests/factories.py
@@ -1,10 +1,11 @@
 import factory
+import factory.fuzzy
 from faker import Faker
 
 from chartofaccountDIT.test.factories import NaturalCodeFactory, ProgrammeCodeFactory
 from costcentre.test.factories import CostCentreFactory
 from gifthospitality.test.factories import GradeFactory
-from payroll.models import Employee, PayElementType, PayElementTypeGroup
+from payroll.models import Employee, PayElementType, PayElementTypeGroup, Vacancy
 
 
 fake = Faker()
@@ -42,3 +43,23 @@ class Meta:
     # name
     natural_code = factory.SubFactory(NaturalCodeFactory)
     group = factory.SubFactory(PayElementTypeGroupFactory)
+
+
+class VacancyFactory(factory.django.DjangoModelFactory):
+    class Meta:
+        model = Vacancy
+
+    cost_centre = factory.SubFactory(CostCentreFactory)
+    programme_code = factory.SubFactory(ProgrammeCodeFactory)
+    grade = factory.SubFactory(GradeFactory)
+    fte = 1.0
+
+    recruitment_type = factory.fuzzy.FuzzyChoice(
+        Vacancy.RecruitmentType.choices, getter=lambda c: c[0]
+    )
+    recruitment_stage = factory.fuzzy.FuzzyChoice(
+        Vacancy.RecruitmentStage.choices, getter=lambda c: c[0]
+    )
+    appointee_name = factory.Faker("name")
+    hiring_manager = factory.Faker("name")
+    hr_ref = factory.Faker("name")
diff --git a/payroll/tests/services/test_payroll.py b/payroll/tests/services/test_payroll.py
index 81778dc5e..589c43afb 100644
--- a/payroll/tests/services/test_payroll.py
+++ b/payroll/tests/services/test_payroll.py
@@ -1,107 +1,138 @@
+from statistics import mean
+
 import pytest
 
 from core.models import FinancialYear
-from payroll.services.payroll import employee_created, payroll_forecast_report
+from costcentre.test.factories import CostCentreFactory
+from payroll.services.payroll import (
+    employee_created,
+    payroll_forecast_report,
+    vacancy_created,
+)
 
-from ..factories import EmployeeFactory, PayElementTypeFactory
+from ..factories import EmployeeFactory, VacancyFactory
 
 
 def test_payroll_forecast(db):
-    SALARY_NAC = "77770001"
-    PENSION_NAC = "77770002"
-
-    salary_1 = PayElementTypeFactory.create(
-        name="Salary 1",
-        group__name="Salary",
-        group__natural_code__natural_account_code=SALARY_NAC,
-    )
-    salary_2 = PayElementTypeFactory.create(
-        name="Salary 2",
-        group__name="Salary",
-        group__natural_code__natural_account_code=SALARY_NAC,
-    )
-    pension_1 = PayElementTypeFactory.create(
-        name="Pension 1",
-        group__name="Pension",
-        group__natural_code__natural_account_code=PENSION_NAC,
+    # NOTE: These must match the PAYROLL.BASIC_PAY_NAC and PAYROLL.PENSION_NAC settings.
+    SALARY_NAC = "71111001"
+    PENSION_NAC = "71111002"
+
+    cost_centre = CostCentreFactory.create(cost_centre_code="123456")
+
+    # salary_1 = PayElementTypeFactory.create(
+    #     name="Salary 1",
+    #     group__name="Salary",
+    #     group__natural_code__natural_account_code=SALARY_NAC,
+    # )
+    # salary_2 = PayElementTypeFactory.create(
+    #     name="Salary 2",
+    #     group__name="Salary",
+    #     group__natural_code__natural_account_code=SALARY_NAC,
+    # )
+    # pension_1 = PayElementTypeFactory.create(
+    #     name="Pension 1",
+    #     group__name="Pension",
+    #     group__natural_code__natural_account_code=PENSION_NAC,
+    # )
+
+    payroll_employee_1 = EmployeeFactory.create(
+        cost_centre=cost_centre,
+        programme_code__programme_code="123456",
+        grade__grade="Grade 7",
+        basic_pay=195000,
+        pension=7550,
+        ernic=0,
     )
-
-    payroll_employees = EmployeeFactory.create_batch(
-        size=2,
-        cost_centre__cost_centre_code="123456",
+    payroll_employee_2 = EmployeeFactory.create(
+        cost_centre=cost_centre,
         programme_code__programme_code="123456",
         grade__grade="Grade 7",
+        basic_pay=152440,
+        pension=11525,
+        ernic=0,
     )
     # non-payroll employees
     _ = EmployeeFactory.create_batch(
         size=2,
-        cost_centre__cost_centre_code="123456",
+        cost_centre=cost_centre,
         programme_code__programme_code="123456",
         grade__grade="Grade 7",
     )
 
     # TODO: Consider an ergonomic way of avoiding this pattern all the time.
-    for x in payroll_employees:
-        employee_created(x)
-
-    payroll_employees[0].pay_element.create(
-        type=salary_1,
-        debit_amount=2000,
-        credit_amount=100,
-    )
-    payroll_employees[0].pay_element.create(
-        type=salary_2,
-        debit_amount=100,
-        credit_amount=50,
-    )
-    payroll_employees[0].pay_element.create(
-        type=pension_1,
-        debit_amount=75.5,
-        credit_amount=0,
+    employee_created(payroll_employee_1)
+    employee_created(payroll_employee_2)
+
+    # payroll_employees[0].pay_element.create(
+    #     type=salary_1,
+    #     debit_amount=2000,
+    #     credit_amount=100,
+    # )
+    # payroll_employees[0].pay_element.create(
+    #     type=salary_2,
+    #     debit_amount=100,
+    #     credit_amount=50,
+    # )
+    # payroll_employees[0].pay_element.create(
+    #     type=pension_1,
+    #     debit_amount=75.5,
+    #     credit_amount=0,
+    # )
+
+    # payroll_employees[1].pay_element.create(
+    #     type=salary_1,
+    #     debit_amount=1500,
+    #     credit_amount=55.6,
+    # )
+    # payroll_employees[1].pay_element.create(
+    #     type=salary_2,
+    #     debit_amount=80,
+    #     credit_amount=0,
+    # )
+    # payroll_employees[1].pay_element.create(
+    #     type=pension_1,
+    #     debit_amount=130.25,
+    #     credit_amount=15,
+    # )
+
+    vacancy = VacancyFactory.create(
+        cost_centre=cost_centre,
+        programme_code__programme_code="123456",
+        grade__grade="Grade 7",
+        fte=0.5,
     )
 
-    payroll_employees[1].pay_element.create(
-        type=salary_1,
-        debit_amount=1500,
-        credit_amount=55.6,
-    )
-    payroll_employees[1].pay_element.create(
-        type=salary_2,
-        debit_amount=80,
-        credit_amount=0,
-    )
-    payroll_employees[1].pay_element.create(
-        type=pension_1,
-        debit_amount=130.25,
-        credit_amount=15,
-    )
+    vacancy_created(vacancy)
 
     financial_year = FinancialYear.objects.current()
 
     # In April, both employees are paid.
     # In May, only the first employee is paid.
-    # In June, neither employee is paid.
-    payroll_employees[0].pay_periods.filter(year=financial_year).update(period_3=False)
-    payroll_employees[1].pay_periods.filter(year=financial_year).update(
+    # In June, neither employee is paid, but the vacancy is filled.
+    payroll_employee_1.pay_periods.filter(year=financial_year).update(period_3=False)
+    payroll_employee_2.pay_periods.filter(year=financial_year).update(
         period_2=False, period_3=False
     )
+    vacancy.pay_periods.filter(year=financial_year).update(period_3=True)
 
-    report = payroll_forecast_report(payroll_employees[0].cost_centre, financial_year)
+    report = payroll_forecast_report(cost_centre, financial_year)
 
-    report_by_name = {x["pay_element__type__group__name"]: x for x in report}
+    report_by_nac = {x["natural_account_code"]: x for x in report}
 
     # eN = employee (e.g. employee 1) / s = salary / p = pension
     # debit_amount - credit_amount
-    e1s = (2000 - 100) + (100 - 50)
-    e1p = 75.5 - 0
-    e2s = (1500 - 55.6) + (80 - 0)
-    e2p = 130.25 - 15
+    e1s = ((2000 - 100) + (100 - 50)) * 100
+    e1p = (75.5 - 0) * 100
+    e2s = ((1500 - 55.6) + (80 - 0)) * 100
+    e2p = (130.25 - 15) * 100
+    v1s = mean([e1s, e2s]) * 0.5
 
     # employee 3 and 4 are non-payroll (no basic pay)
 
-    assert float(report_by_name["Salary"]["period_1_sum"]) == pytest.approx(e1s + e2s)
-    assert float(report_by_name["Pension"]["period_1_sum"]) == pytest.approx(e1p + e2p)
-    assert float(report_by_name["Salary"]["period_2_sum"]) == pytest.approx(e1s)
-    assert float(report_by_name["Pension"]["period_2_sum"]) == pytest.approx(e1p)
-    assert float(report_by_name["Salary"]["period_3_sum"]) == pytest.approx(0)
-    assert float(report_by_name["Pension"]["period_3_sum"]) == pytest.approx(0)
+    assert float(report_by_nac[SALARY_NAC]["apr"]) == pytest.approx(e1s + e2s)
+    assert float(report_by_nac[PENSION_NAC]["apr"]) == pytest.approx(e1p + e2p)
+    assert float(report_by_nac[SALARY_NAC]["may"]) == pytest.approx(e1s)
+    assert float(report_by_nac[PENSION_NAC]["may"]) == pytest.approx(e1p)
+    assert float(report_by_nac[SALARY_NAC]["jun"]) == pytest.approx(v1s)
+    assert float(report_by_nac[PENSION_NAC]["jun"]) == pytest.approx(0)
diff --git a/poetry.lock b/poetry.lock
index ce9811eb6..80cf3bff7 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,4 +1,4 @@
-# This file is automatically @generated by Poetry 1.8.3 and should not be changed by hand.
+# This file is automatically @generated by Poetry 1.8.4 and should not be changed by hand.
 
 [[package]]
 name = "amqp"
@@ -1660,6 +1660,70 @@ files = [
     {file = "nodeenv-1.9.1.tar.gz", hash = "sha256:6ec12890a2dab7946721edbfbcd91f3319c6ccc9aec47be7c7e6b7011ee6645f"},
 ]
 
+[[package]]
+name = "numpy"
+version = "2.1.3"
+description = "Fundamental package for array computing in Python"
+optional = false
+python-versions = ">=3.10"
+files = [
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 [[package]]
 name = "oauthlib"
 version = "3.2.2"
@@ -2917,4 +2981,4 @@ type = ["pytest-mypy"]
 [metadata]
 lock-version = "2.0"
 python-versions = "^3.12"
-content-hash = "8ab5c01c4bfa95c5030e54b9dca2a24e0efc784e4bb5dea7df63d26cc612c626"
+content-hash = "19494c699d8c02c3ca4983dc8945a3138313220d3dcdd26124797c23c8dd1c06"
diff --git a/pyproject.toml b/pyproject.toml
index a56f018bf..16a00a762 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -39,6 +39,7 @@ openpyxl = "^3.0.5"
 requests = "^2.32.0"
 redis = "^5.0.3"
 granian = "^1.6.3"
+numpy = "^2.1.3"
 
 # Are these packages still needed?
 django-import-export = "^3.3.07"
@@ -72,7 +73,7 @@ pyperclip = "^1.8.0"
 freezegun = "^1.0.0"
 isort = "^5.10.1"
 ruff = "^0.3.4"
-mypy = "^1.12.0"
+mypy = "^1.13.0"
 
 [build-system]
 requires = ["poetry-core"]
@@ -126,3 +127,6 @@ minversion = "7.0"
 addopts = "--ignore=front_end --ignore=features --ignore=staticfiles --ds=config.settings.ci --reuse-db"
 python_files = ["test_*.py", "*_test.py", "tests.py"]
 filterwarnings = ["ignore::DeprecationWarning"]
+
+[tool.mypy]
+enable_incomplete_feature = ["NewGenericSyntax"]