diff --git a/.changeset/ninety-rats-retire.md b/.changeset/ninety-rats-retire.md
new file mode 100644
index 0000000000..d6e3ab7295
--- /dev/null
+++ b/.changeset/ninety-rats-retire.md
@@ -0,0 +1,5 @@
+---
+'@lion/ui': patch
+---
+
+[input-amount] returns Unparseable as a modelValue if a wrong value has been entered
diff --git a/docs/components/input-amount/overview.md b/docs/components/input-amount/overview.md
index 158121389f..8a2c988c6a 100644
--- a/docs/components/input-amount/overview.md
+++ b/docs/components/input-amount/overview.md
@@ -4,7 +4,7 @@ A web component based on the generic text input field. Its purpose is to provide
 
 For formatting, we use [Intl NumberFormat](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/NumberFormat) with some overrides.
 
-For parsing user input, we provide our own parser that takes into account a number of heuristics, locale and ignores invalid characters.
+For parsing user input, we provide our own parser that takes into account locale, a number of heuristics and allows for pasting amount strings like 'EUR 100,00'.
 Valid characters are digits and separators. Formatting happens on-blur.
 
 If there are no valid characters in the input whatsoever, it will provide an error feedback.
diff --git a/packages/ui/components/input-amount/src/parsers.js b/packages/ui/components/input-amount/src/parsers.js
index be422f2c2c..ecd80dcc11 100644
--- a/packages/ui/components/input-amount/src/parsers.js
+++ b/packages/ui/components/input-amount/src/parsers.js
@@ -11,7 +11,8 @@ import { parseNumber, getFractionDigits } from '@lion/ui/localize-no-side-effect
  * @return {number} new value with rounded up decimals
  */
 function round(value, decimals) {
-  if (typeof decimals === 'undefined') {
+  const numberContainsExponent = value?.toString().includes('e');
+  if (typeof decimals === 'undefined' || numberContainsExponent) {
     return Number(value);
   }
   return Number(`${Math.round(Number(`${value}e${decimals}`))}e-${decimals}`);
@@ -30,10 +31,17 @@ function round(value, decimals) {
  * @param {FormatOptions} [givenOptions] Locale Options
  */
 export function parseAmount(value, givenOptions) {
+  const unmatchedInput = value.match(/[^0-9,.\- ]/g);
+  // for the full paste behavior documentation:
+  // ./docs/components/input-amount/use-cases.md#paste-behavior
+  if (unmatchedInput && givenOptions?.mode !== 'pasted') {
+    return undefined;
+  }
+
   const number = parseNumber(value, givenOptions);
 
-  if (typeof number !== 'number') {
-    return number;
+  if (typeof number !== 'number' || Number.isNaN(number)) {
+    return undefined;
   }
 
   /** @type {FormatOptions} */
diff --git a/packages/ui/components/input-amount/test/formatters.test.js b/packages/ui/components/input-amount/test/formatters.test.js
index feefc3f8b4..0488b7ae8c 100644
--- a/packages/ui/components/input-amount/test/formatters.test.js
+++ b/packages/ui/components/input-amount/test/formatters.test.js
@@ -74,4 +74,15 @@ describe('formatAmount()', () => {
     localizeManager.locale = 'nl-NL';
     expect(formatAmount(12345678)).to.equal('12.345.678,00');
   });
+
+  // TODO: make it work with big numbers, e.g. make use of BigInt
+  it.skip('rounds up big numbers', async () => {
+    expect(formatAmount(1e21, { locale: 'en-GB', currency: 'EUR' })).to.equal(
+      '1,000,000,000,000,000,000,000.00',
+    );
+    // eslint-disable-next-line no-loss-of-precision
+    expect(formatAmount(12345678987654321.42, { locale: 'en-GB', currency: 'EUR' })).to.equal(
+      '12,345,678,987,654,321.42',
+    );
+  });
 });
diff --git a/packages/ui/components/input-amount/test/parsers.test.js b/packages/ui/components/input-amount/test/parsers.test.js
index 2af83baabc..6cd58449c5 100644
--- a/packages/ui/components/input-amount/test/parsers.test.js
+++ b/packages/ui/components/input-amount/test/parsers.test.js
@@ -1,11 +1,20 @@
 import { expect } from '@open-wc/testing';
-import { localize } from '@lion/ui/localize.js';
-
+import { getLocalizeManager } from '@lion/ui/localize-no-side-effects.js';
+import { localizeTearDown } from '@lion/ui/localize-test-helpers.js';
 import { parseAmount } from '@lion/ui/input-amount.js';
 
 describe('parseAmount()', async () => {
+  const localizeManager = getLocalizeManager();
+
+  beforeEach(() => {
+    localizeManager.locale = 'en-GB';
+  });
+
+  afterEach(() => {
+    localizeTearDown();
+  });
+
   it('with currency set to correct amount of decimals', async () => {
-    localize.locale = 'en-GB';
     expect(
       parseAmount('1.015', {
         currency: 'EUR',
@@ -29,7 +38,26 @@ describe('parseAmount()', async () => {
   });
 
   it('with no currency keeps all decimals', async () => {
-    localize.locale = 'en-GB';
     expect(parseAmount('1.015')).to.equal(1.015);
   });
+
+  // TODO: make it work with big numbers, e.g. make use of BigInt
+  it.skip('rounds up big numbers', async () => {
+    // eslint-disable-next-line no-loss-of-precision
+    expect(parseAmount('999999999999999999999,42')).to.equal(999999999999999999999.42);
+    // eslint-disable-next-line no-loss-of-precision
+    expect(parseAmount('12,345,678,987,654,321.42')).to.equal(12345678987654321.42);
+  });
+
+  it('returns undefined if an invalid value is entered', async () => {
+    expect(parseAmount('foo')).to.equal(undefined);
+    expect(parseAmount('foo1')).to.equal(undefined);
+    expect(parseAmount('EUR 1,50')).to.equal(undefined);
+    expect(parseAmount('--1')).to.equal(undefined);
+  });
+
+  it('ignores letters when "pasted" mode used', async () => {
+    expect(parseAmount('foo1', { mode: 'pasted' })).to.equal(1);
+    expect(parseAmount('EUR 1,50', { mode: 'pasted' })).to.equal(1.5);
+  });
 });
diff --git a/packages/ui/components/localize/src/number/formatNumber.js b/packages/ui/components/localize/src/number/formatNumber.js
index 1c7ee984e1..e75decbaa9 100644
--- a/packages/ui/components/localize/src/number/formatNumber.js
+++ b/packages/ui/components/localize/src/number/formatNumber.js
@@ -26,7 +26,7 @@ export function formatNumber(number, options = /** @type {FormatOptions} */ ({})
   }
   let printNumberOfParts = '';
   // update numberOfParts because there may be some parts added
-  const numberOfParts = formattedToParts && formattedToParts.length;
+  const numberOfParts = formattedToParts ? formattedToParts.length : 0;
   for (let i = 0; i < numberOfParts; i += 1) {
     const part = /** @type {FormatNumberPart} */ (formattedToParts[i]);
     printNumberOfParts += part.value;
diff --git a/packages/ui/components/localize/test/number/formatNumber.test.js b/packages/ui/components/localize/test/number/formatNumber.test.js
index 8c5f963c28..7237defa24 100644
--- a/packages/ui/components/localize/test/number/formatNumber.test.js
+++ b/packages/ui/components/localize/test/number/formatNumber.test.js
@@ -246,6 +246,15 @@ Please specify .groupSeparator / .decimalSeparator on the formatOptions object t
     });
   });
 
+  // TODO: make it work with big numbers, e.g. make use of BigInt
+  it.skip('can handle big numbers', async () => {
+    expect(formatNumber(1e21)).to.equal('1,000,000,000,000,000,000,000');
+    // eslint-disable-next-line no-loss-of-precision
+    expect(formatNumber(999999999999999999999.42)).to.equal('999,999,999,999,999,999,999.42');
+    // eslint-disable-next-line no-loss-of-precision
+    expect(formatNumber(12345678987654321.42)).to.equal('12,345,678,987,654,321.42');
+  });
+
   describe('normalization', () => {
     describe('en-GB', () => {
       it('supports basics', () => {