diff --git a/projects/demo-integrations/cypress/tests/kit/number/number-prefix-postfix.cy.ts b/projects/demo-integrations/cypress/tests/kit/number/number-prefix-postfix.cy.ts
index 032a8ef4b..e24a15630 100644
--- a/projects/demo-integrations/cypress/tests/kit/number/number-prefix-postfix.cy.ts
+++ b/projects/demo-integrations/cypress/tests/kit/number/number-prefix-postfix.cy.ts
@@ -1,5 +1,6 @@
 import {DemoPath} from '@demo/constants';
 
+import {BROWSER_SUPPORTS_REAL_EVENTS} from '../../../support/constants';
 import {openNumberPage} from './utils';
 
 describe('Number | Prefix & Postfix', () => {
@@ -179,18 +180,88 @@ describe('Number | Prefix & Postfix', () => {
         });
     });
 
-    describe('works if the same character ends/starts', () => {
-        describe('[prefix]="$_" | [postfix]="_per_day"', () => {
+    describe('prefix/postfix ends/starts with the same character', () => {
+        describe('[prefix]="$_" | [postfix]="_per_day" (with caret guard)', () => {
             beforeEach(() => {
                 openNumberPage('prefix=$_&postfix=_per_day');
+
+                cy.get('@input')
+                    .should('have.value', '$__per_day')
+                    .should('have.prop', 'selectionStart', '$_'.length)
+                    .should('have.prop', 'selectionEnd', '$_'.length);
             });
 
-            // TODO
-            it('$_|_per_day => Type Backspace => $_|_per_day', () => {});
+            it('$_|_per_day => Type Backspace => $_|_per_day', () => {
+                cy.get('@input')
+                    .type('{backspace}')
+                    .should('have.value', '$__per_day')
+                    .should('have.prop', 'selectionStart', '$_'.length)
+                    .should('have.prop', 'selectionEnd', '$_'.length);
+            });
+
+            it('$_|_per_day => Type Delete => $_|_per_day', () => {
+                cy.get('@input')
+                    .type('{del}')
+                    .should('have.value', '$__per_day')
+                    .should('have.prop', 'selectionStart', '$_'.length)
+                    .should('have.prop', 'selectionEnd', '$_'.length);
+            });
 
-            it('$_|_per_day => Type Delete => $_|_per_day', () => {});
+            it('$_|_per_day => Select all + Delete => $_|_per_day', () => {
+                cy.get('@input')
+                    .type('{selectAll}{del}')
+                    .should('have.value', '$__per_day')
+                    .should('have.prop', 'selectionStart', '$_'.length)
+                    .should('have.prop', 'selectionEnd', '$_'.length);
+            });
+        });
 
-            it('$_|_per_day => Select all + Delete => $_|_per_day', () => {});
+        describe('[prefix]="$ " | [postfix]=" per day" (without caret guard)', () => {
+            beforeEach(() => {
+                cy.visit(DemoPath.Cypress);
+                cy.get('#mirrored-prefix-postfix input')
+                    .focus()
+                    .type('{selectAll}{del}')
+                    .should('have.value', '$  per day')
+                    .should('have.prop', 'selectionStart', '$ '.length)
+                    .should('have.prop', 'selectionEnd', '$ '.length)
+                    .as('input');
+            });
+
+            it('$  per day| => Type Backspace => $  per da|y', () => {
+                cy.get('@input')
+                    .type('{moveToEnd}')
+                    .type('{backspace}')
+                    .should('have.value', '$  per day')
+                    .should('have.prop', 'selectionStart', '$  per da'.length)
+                    .should('have.prop', 'selectionEnd', '$  per da'.length);
+            });
+
+            it('$  per da|y => Type Backspace => $  per d|ay', () => {
+                cy.get('@input')
+                    .type('{moveToEnd}{leftArrow}')
+                    .type('{backspace}')
+                    .should('have.value', '$  per day')
+                    .should('have.prop', 'selectionStart', '$  per d'.length)
+                    .should('have.prop', 'selectionEnd', '$  per d'.length);
+            });
+
+            it(
+                '$  p|er |day => Type Backspace => $  p|er da|y',
+                BROWSER_SUPPORTS_REAL_EVENTS,
+                () => {
+                    cy.get('@input')
+                        .type('{moveToEnd}')
+                        .type('{leftArrow}'.repeat('day'.length))
+                        .realPress(['Shift', ...Array('1.1'.length).fill('ArrowLeft')]);
+
+                    cy.get('@input')
+                        .type('{backspace}')
+                        .should('have.value', '$  per day')
+                        .should('have.prop', 'selectionStart', '$  p'.length)
+                        .should('have.prop', 'selectionEnd', '$  p'.length);
+                },
+            );
         });
     });
 });
diff --git a/projects/demo/src/pages/cypress/examples/3-mirrored-prefix-postfix/component.ts b/projects/demo/src/pages/cypress/examples/3-mirrored-prefix-postfix/component.ts
index 5da7d4c79..68087e81b 100644
--- a/projects/demo/src/pages/cypress/examples/3-mirrored-prefix-postfix/component.ts
+++ b/projects/demo/src/pages/cypress/examples/3-mirrored-prefix-postfix/component.ts
@@ -6,7 +6,7 @@ import {maskitoNumberOptionsGenerator} from '@maskito/kit';
     selector: 'test-doc-example-3',
     template: `
         <input
-            value="$ 100 per kg"
+            value="$ 100 per day"
             [maskito]="numberMask"
         />
     `,
@@ -15,6 +15,6 @@ import {maskitoNumberOptionsGenerator} from '@maskito/kit';
 export class TestDocExample3 {
     readonly numberMask: MaskitoOptions = maskitoNumberOptionsGenerator({
         prefix: '$ ',
-        postfix: ' per kg',
+        postfix: ' per day',
     });
 }
diff --git a/projects/kit/src/lib/processors/postfix-postprocessor.ts b/projects/kit/src/lib/processors/postfix-postprocessor.ts
index eaba67934..4d3457802 100644
--- a/projects/kit/src/lib/processors/postfix-postprocessor.ts
+++ b/projects/kit/src/lib/processors/postfix-postprocessor.ts
@@ -1,14 +1,16 @@
 import {MaskitoPostprocessor} from '@maskito/core';
 
-import {escapeRegExp, identity} from '../utils';
+import {escapeRegExp, findCommonBeginningSubstr, identity} from '../utils';
 
 export function maskitoPostfixPostprocessorGenerator(
     postfix: string,
 ): MaskitoPostprocessor {
+    const postfixRE = new RegExp(`${escapeRegExp(postfix)}$`);
+
     return postfix
         ? ({value, selection}, initialElementState) => {
               if (!value && !initialElementState.value.endsWith(postfix)) {
-                  // cases when developer wants input to be empty
+                  // cases when developer wants input to be empty (programmatically)
                   return {value, selection};
               }
 
@@ -20,10 +22,15 @@ export function maskitoPostfixPostprocessorGenerator(
               }
 
               const initialValueBeforePostfix = initialElementState.value.replace(
-                  new RegExp(`${escapeRegExp(postfix)}$`),
+                  postfixRE,
                   '',
               );
-              const untouchedPart = getUntouched(initialValueBeforePostfix, value);
+              const postfixWasModified =
+                  initialElementState.selection[1] >= initialValueBeforePostfix.length;
+              const alreadyExistedValueBeforePostfix = findCommonBeginningSubstr(
+                  initialValueBeforePostfix,
+                  value,
+              );
 
               return {
                   selection,
@@ -31,8 +38,11 @@ export function maskitoPostfixPostprocessorGenerator(
                       .reverse()
                       .reduce((newValue, char, index) => {
                           const i = newValue.length - 1 - index;
+                          const isInitiallyMirroredChar =
+                              alreadyExistedValueBeforePostfix[i] === char &&
+                              postfixWasModified;
 
-                          return newValue[i] !== char || untouchedPart[i] === char
+                          return newValue[i] !== char || isInitiallyMirroredChar
                               ? newValue.slice(0, i + 1) + char + newValue.slice(i + 1)
                               : newValue;
                       }, value),
@@ -40,17 +50,3 @@ export function maskitoPostfixPostprocessorGenerator(
           }
         : identity;
 }
-
-function getUntouched(initial: string, now: string): string {
-    let res = '';
-
-    for (let i = 0; i < now.length; i++) {
-        if (now[i] !== initial[i]) {
-            return res;
-        }
-
-        res += now[i];
-    }
-
-    return res;
-}
diff --git a/projects/kit/src/lib/utils/find-common-beginning-substr.ts b/projects/kit/src/lib/utils/find-common-beginning-substr.ts
new file mode 100644
index 000000000..64256a7a2
--- /dev/null
+++ b/projects/kit/src/lib/utils/find-common-beginning-substr.ts
@@ -0,0 +1,13 @@
+export function findCommonBeginningSubstr(a: string, b: string): string {
+    let res = '';
+
+    for (let i = 0; i < a.length; i++) {
+        if (a[i] !== b[i]) {
+            return res;
+        }
+
+        res += a[i];
+    }
+
+    return res;
+}
diff --git a/projects/kit/src/lib/utils/index.ts b/projects/kit/src/lib/utils/index.ts
index a2abdbab1..93838d748 100644
--- a/projects/kit/src/lib/utils/index.ts
+++ b/projects/kit/src/lib/utils/index.ts
@@ -9,6 +9,7 @@ export * from './date/segments-to-date';
 export * from './date/to-date-string';
 export * from './date/validate-date-string';
 export * from './escape-reg-exp';
+export * from './find-common-beginning-substr';
 export * from './get-focused';
 export * from './get-object-from-entries';
 export * from './identity';
diff --git a/projects/kit/src/lib/utils/tests/find-common-beginning-substr.spec.ts b/projects/kit/src/lib/utils/tests/find-common-beginning-substr.spec.ts
new file mode 100644
index 000000000..92372cb84
--- /dev/null
+++ b/projects/kit/src/lib/utils/tests/find-common-beginning-substr.spec.ts
@@ -0,0 +1,20 @@
+import {findCommonBeginningSubstr} from '../find-common-beginning-substr';
+
+describe('findCommonBeginningSubstr', () => {
+    it('returns common substring until all characters are equal', () => {
+        expect(findCommonBeginningSubstr('123_456', '123456')).toBe('123');
+    });
+
+    it('returns empty string if any string is empty', () => {
+        expect(findCommonBeginningSubstr('123_456', '')).toBe('');
+        expect(findCommonBeginningSubstr('', '123_456')).toBe('');
+    });
+
+    it('returns empty string if the first characters are different', () => {
+        expect(findCommonBeginningSubstr('012345', '123')).toBe('');
+    });
+
+    it('returns the whole string if all characters are equal', () => {
+        expect(findCommonBeginningSubstr('777999', '777999')).toBe('777999');
+    });
+});