diff --git a/service/constants.py b/service/constants.py
index 56e1eae..554e3c6 100644
--- a/service/constants.py
+++ b/service/constants.py
@@ -27,6 +27,6 @@
 DEPT_ID_LEN = 5
 MUNI_ID_LEN = 6
 CENSUS_LOCALITY_ID_LEN = 8
-SETTLEMENT_ID_LEN = 11
-LOCALITY_ID_LEN = SETTLEMENT_ID_LEN
+SETTLEMENT_ID_LEN = 10
+LOCALITY_ID_LEN = 11
 STREET_ID_LEN = 13
diff --git a/service/params.py b/service/params.py
index 6bc6b45..4179041 100644
--- a/service/params.py
+++ b/service/params.py
@@ -313,6 +313,30 @@ def _parse_value(self, val):
         return list(ids)
 
 
+class IdsAlphamericParameter(IdsParameter):
+
+    def _parse_value(self, val):
+        items = val.split(self._sep)
+        if len(items) > constants.MAX_RESULT_LEN:
+            raise ValueError(strings.ID_PARAM_LENGTH.format(
+                constants.MAX_RESULT_LEN))
+
+        ids = set()
+        for item in items:
+            item = item.strip()
+
+            if len(item) > self._id_length or len(item) < self._min_length:
+                raise ValueError(strings.ID_ALPHAMERIC_PARAM_INVALID.format(
+                    self._min_length, self._id_length))
+
+            if item in ids:
+                raise ValueError(strings.ID_PARAM_UNIQUE.format(item))
+
+            ids.add(item)
+
+        return list(ids)
+
+
 class CompoundParameter(Parameter):
     """Representa un parámetro que puede tomar distintos valores, representados
     por una lista de objetos 'Parameter'.
@@ -1188,7 +1212,7 @@ def parse_get_params(self, qs_params):
 )
 
 PARAMS_SETTLEMENTS = EndpointParameters(shared_params={
-    N.ID: IdsParameter(id_length=constants.SETTLEMENT_ID_LEN),
+    N.ID: IdsAlphamericParameter(id_length=constants.SETTLEMENT_ID_LEN, padding_length=2),
     N.NAME: StrParameter(),
     N.STATE: CompoundParameter([IdsParameter(constants.STATE_ID_LEN),
                                 StrParameter()]),
diff --git a/service/strings.py b/service/strings.py
index 4a1e365..29abf85 100644
--- a/service/strings.py
+++ b/service/strings.py
@@ -33,6 +33,7 @@
 NOT_FOUND = 'No se encontró la URL especificada.'
 NOT_ALLOWED = 'Método no permitido en el recurso seleccionado.'
 ID_PARAM_INVALID = 'Cada ID debe ser numérico y de longitud {}.'
+ID_ALPHAMERIC_PARAM_INVALID = 'Cada ID debe ser de longitud entre {} y {}.'
 ID_PARAM_LENGTH = 'La cantidad de ID debe ser menor o igual que {}.'
 ID_PARAM_UNIQUE = 'La lista no debe contener ID repetidos (ID repetido: {}).'
 COMPOUND_PARAM_ERROR = 'El valor del parámetro no es válido.'