Why 1C Does Not Calculate IIT: Main Reasons and Carry-Forward Deductions
How to Check the IIT Calculation (Step-by-Step Algorithm)
To make sure the program is working correctly and not producing an error, perform a check using the registers and documents:
Open the document "Calculation of Employee Deductions" for the current month. Go to the "Income Tax" tab and check for the presence of the calculation base.
Generate the "Tax Accounting Register for IIT and SocTax" report for this employee for the previous and current months.
In the generated register, find the income and applied deductions columns. If in the previous period the amount in the deductions column exceeds the income amount, the difference formed the carry-forward balance.
Check the validity of the "Application for IIT Deductions" document. Make sure its validity period covers the current month.
Additional Reasons for the Absence of Tax
If there is definitely no carry-forward deduction, but the tax is still not calculated, check the following settings:
Posting chronology is broken: Income and deduction data were entered out of order. The program may be taking balances from the wrong period. Solution — undo the posting and re-post the accruals strictly by month.
Accrual type settings: In the accrual card (for example, a one-time bonus or material assistance) on the "Accounting" tab, the relation to IIT is specified incorrectly (indicating that the income is fully or partially not taxable).
Outdated configuration release: In older releases, the calculation algorithms may not account for the latest legislative changes, or may contain software errors.
FAQ
Is this a bug in 1C? No, this is the calculation mechanism working correctly. The legislation allows the unused amount of standard deductions to be carried forward to subsequent periods within the current calendar year.
Do the registers or the amount need to be adjusted manually? It is strongly not recommended to interfere with the calculation using manual adjustments. If the primary data (salaries, deduction applications) is entered correctly, 1C will offset the carry-forward deduction on its own. Manual edits will lead to "broken" balances in settlements with the budget in subsequent months.
Why was IIT calculated, but the amount is less than expected? The taxable base was partially offset by the balance from the previous month. The program deducted MPC, CSHI, the current month's standard deduction, and then deducted the "tail" of the previous period's deduction, which reduced the final base.
Do unused deductions expire at the end of the year? Yes. Deduction carry-forward only works within a single tax period. Unused balances for December do not carry over to January of the following year.