Tax loss carryforward in Poland: prepare your PIT deduction with AI

A Polish sole trader can carry a business tax loss forward against income from the same source over the next five tax years, subject to limits. AI can help reconcile tax returns, deductions already claimed and the remaining balance. It should not invent an earlier loss or assume that the full amount on an old PIT return is still available. Preparing the deduction starts with the history of your tax returns, before calculating this year's tax.

This guide concerns a Polish sole proprietorship, or JDG, preparing a PIT return, primarily under the progressive scale or flat income tax. It does not cover a limited company's CIT losses or investment losses reported in PIT-38. The legal position was checked on 6 November 2026.

What is a tax loss, and what remains available?

A tax loss arises when tax-deductible costs from an income source exceed its revenue for the tax year. It is a tax result, not a negative bank balance, a cash shortage or the total of unpaid bills. Start with the correctly determined annual result reported in the return, taking any amendments into account.

Keep three figures separate: the original loss, deductions already claimed and the remaining amount. An original loss of PLN 60,000 with PLN 20,000 previously deducted leaves PLN 40,000. That does not necessarily make all PLN 40,000 deductible this year. You must also check the applicable limit, available income and expiry year.

Use a separate row for every loss year. Combining everything into one “loss available” figure hides which balance expires first. The governing rules are in Article 9(2) and (3) of Poland's Personal Income Tax Act.

How much can you deduct, and for how long?

There are two methods for the recent business losses discussed here. You can deduct amounts over subsequent years, with a limit of 50% of the original loss in any one year. Alternatively, you can make a one-off deduction of up to PLN 5 million in one of the next five tax years. Any balance is deductible in other years within that same window, with a yearly cap of 50% of the original loss.

The five years start with the tax year after the loss arose. For a loss incurred in 2021, the relevant years are 2022, 2023, 2024, 2025 and 2026. The return for 2026 is the last one within that window, even if you submit that return in 2027. For a loss incurred in 2024, the final deduction year is 2029.

The deduction is also restricted by income from the relevant source and the unused balance. Carrying forward an earlier loss cannot create a new loss for the current year. The PLN 5 million limit is not an automatic refund or an amount every business can enter. The Ministry of Finance explains the rules and examples in its PIT loss deduction guide.

Which documents should you prepare for an AI review?

Collect the filed return for the loss year and returns for later years in which you may have used it. Include amendments. Avoid mixing an original return for one year with an amended version for another without identifying the difference. Retain the document reference and version date. Tax payment transfers alone do not reveal how much of a loss was deducted.

Prepare a working schedule containing:

1. Loss year and source: keep different income sources separate.
2. Original amount: reconcile it to the correct return and accounting records.
3. Deductions by year: link each amount to its supporting tax calculation or return.
4. Deduction method: record whether the one-off option was used, and when.
5. Remaining balance and final year: calculate these separately for each loss year.
6. Current-year figures: include income and any loss already used in advance tax calculations.

Mark a missing document as “needs clarification”. Do not substitute zero: zero is a confirmed amount, whereas missing information is unknown. If you moved to a new bookkeeping system, the history before that move still matters.

Example: two losses and one income figure

These figures are illustrative and do not describe a Norman customer. Assume that 2026 business income available for loss deductions in this simplified example is PLN 35,000. We leave other deductions and special adjustments out of the calculation.

Assume earlier deductions of the 2021 loss respected the annual 50% cap. For the 2024 loss, the trader used a one-off deduction of PLN 20,000 in 2025. The subsequent annual cap for that second loss is therefore PLN 30,000, which is 50% of the original PLN 60,000.

One permissible option for 2026 is PLN 10,000 from the 2021 loss and PLN 25,000 from the 2024 loss. The total deduction is PLN 35,000, limited to the assumed income. The older loss is fully used, while PLN 15,000 of the newer loss remains for the remaining years in its window, subject to the conditions being met.

AI should explain why the full PLN 50,000 balance cannot be deducted: it would exceed income. It should also flag that the older loss is reaching its final eligible year. This checks whether an option is valid; it does not automatically select the most advantageous tax outcome. Other reliefs and the taxpayer's circumstances can change the decision.

How should you ask AI to check the deduction?

Give the assistant structured information and a defined task. A useful result identifies the source of each figure, the limit applied and unresolved gaps. For example:

Prepare a business loss schedule for review before my Polish PIT return for 2026. For each loss year, show the original loss, earlier deductions, remaining balance, final eligible year and 2026 limit. Identify the supporting document for every amount. Do not fill gaps with assumptions. Separate amounts already included in advance payments from any additional deduction and flag decisions that need review.

Look especially for duplicate use: the same loss may appear in a monthly calculation and in the annual return. These are not automatically two separate deductions. The Ministry of Finance allows a loss to be taken into account in advance tax calculations or only in the annual return. The annual calculation must reconcile the overall amount without adding an already-used deduction again.

AI can compare figures and identify a discrepancy. Establishing the correct return version, confirming completeness and choosing the deduction method still require checking documents and making a taxpayer decision. If the source or amount of a loss is disputed, resolve it with your accountant before entering the deduction.

How can you use the reconciled figures in Norman?

Norman's annual PIT preparation workflow includes prior-year losses in the deductions step. Income comes from bookkeeping records and approved operations. Check the historical loss balance against earlier returns; connecting a bank account does not reconstruct that history.

The schedule and AI prompt above describe a way to prepare your inputs. They are not a claim that Norman automatically imports historical returns. Once the deduction is reconciled, review the tax calculation and advance payments. The current instructions provide for downloading an XML file and submitting the return yourself. Preparing a file, submitting a declaration and paying any tax due are separate actions.

For the wider process, read how AI prepares taxes for a Polish sole trader and how closing inventory affects taxable income. Establish the current-year figures and remaining loss balances first, then review the return. This gives you a clear basis for checking tax preparation assisted by AI.