---
title: "Why the IIT (Individual Income Tax) and the amount payable change when calculating salary"
country: KZ
lang: en
author: Сапа Т.И. (https://buhgpt.kz/authors/sapa-ti)
date: 2026-09-23
canonical: https://buhgpt.kz/suraqtar/pochemu-menyaetsya-ipn-i-summa-k-vyplate-pri-raschete-zar-en
source: BuhGPT
---

# Why the IIT (Individual Income Tax) and the amount payable change when calculating salary

> **TL;DR:** The reason for the incorrect calculation of IIT was an incorrectly set date of the employee's application for a tax deduction: it was not indicated from the date of hire. Because of this, in February the deduction was not applied in full, and the remaining part was automatical

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The reason for the incorrect calculation of IIT was an incorrectly set date of the employee's application for a tax deduction: it was not indicated from the date of hire. Because of this, in February the deduction was not applied in full, and the remaining part was automatically carried over to the following months. It was this carryover that affected the IIT amounts in March and April — in one month the tax turned out smaller, in another larger.

How to fix this

It is necessary to check the date of the employee's deduction application and bring it into line with the actual date of hire. In the case under consideration, the employee was hired on February 24 — accordingly, the application date was corrected to that exact date. After that, it was necessary to perform a payroll recalculation for the corresponding periods. After the recalculation, IIT began to be calculated correctly, without carrying over deduction balances and the related jumps in the amount to be paid.

About the discrepancy with the previously paid amount

It is worth separately clarifying a point that often raises questions: IIT is not added to the employee's salary, but is withheld from it during calculation. If the employee was previously paid an amount different from the one calculated by the system (for example, due to an incorrect deduction), the discrepancy arises precisely because of this difference between the amount actually paid earlier and the amount calculated by the program after the deduction date was corrected.

Frequently asked questions

Why wasn't the deduction applied in full right away? Because the application date was indicated later than the hire date, and the system could not correctly distribute the deduction from the beginning of the period — part of it "got stuck" and was carried over to the following months.

Does the recalculation need to be done manually for each month? After correcting the application date, the payroll recalculation is performed for the employee for the affected periods — then the IIT and the amounts to be paid are automatically recalculated correctly.

What if the amount to be paid still doesn't match the expected one? It is worth checking whether the previously actually paid amount differs from the amount calculated by the system — the discrepancy is usually explained by this, rather than by an error in the current IIT calculation.

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