Closing inventory and Polish income tax: preparing the data with AI

For a Polish sole trader keeping a KPiR, closing inventory above opening inventory increases business income; a lower closing figure reduces it. AI can help organise the table, identify missing data and check the calculation. You must establish actual quantities, condition and the correct valuation from the physical inventory and supporting records. Adding up payments from your bank account is not enough to prepare an accurate annual PIT return.

This guide covers the income-tax inventory, or spis z natury, for an entrepreneur using Poland’s tax revenue and expense ledger, the KPiR. It does not cover inventory procedures in a sp. z o.o.’s full accounting books or a liquidation inventory for VAT. We checked the legal sources on 5 November 2026.

Why does inventory change income in a KPiR?

An inventory, commonly called remanent, records the relevant items at a particular date. For a KPiR, these include merchandise, materials, semi-finished products, work in progress, finished products, defective items and waste. It is neither a list of everything purchased nor the balance of a bank account.

The purchase of goods may already appear in costs even though those goods remain on the shelf. Comparing opening and closing inventory adjusts income for the change in that stock. The rule comes from Article 24(2) of Poland’s PIT Act.

For a simple case without additional adjustments, the calculation is:

Income = revenue − costs before the inventory adjustment + closing inventory − opening inventory.

The costs in that formula must not already include the same inventory adjustment. If your software shows income after applying it, adding the difference again would misstate the result. Establish which figure you have before asking an AI assistant to analyse the statement.

Example: how much does income increase?

Suppose a sole trader keeping a KPiR has PLN 200,000 in revenue. Costs before the inventory adjustment are PLN 120,000, opening inventory is PLN 10,000 and closing inventory is PLN 18,000. These are illustrative figures, not a Norman customer’s results.

PLN 8,000 is the increase in income, not the amount of tax payable. Tax also depends on the taxation method, deductions and other information in the return. In the reverse case, with opening inventory of PLN 18,000 and closing inventory of PLN 10,000, the same revenue and costs would produce income of PLN 72,000.

The example excludes cash-basis PIT and special cost adjustments. Do not apply it directly to ryczałt: that tax generally uses revenue rather than income calculated under this formula. It also does not calculate health insurance contributions. Establish the correct result for your tax records first, then complete the relevant calculation.

When must you count and value the inventory?

For a continuing business keeping a KPiR, the inventory is prepared at the end of the tax year. For the 2026 annual settlement, that means the position on 31 December 2026. Other events, including starting or closing a business, can require an inventory at a different date.

You must complete the valuation within 14 days after finishing the inventory. This is a valuation deadline, not permission to ignore the stock position on the required date. The requirements are in sections 20 to 22 of the KPiR regulation effective from 2026.

You can prepare the worksheet and supporting records earlier. Keep a November forecast separate from the final December inventory, however. Goods may be sold, returned or damaged between those dates. These are different versions of the data, which an AI assistant should not combine into one result.

What data should you prepare for an AI check?

Start with the previous inventory, the current inventory worksheet and records supporting the prices. Each line should have an identifier, description, unit, counted quantity, valuation basis and value. Keep the connection between each price and its source document. A number without its origin cannot be checked properly.

Materials and merchandise are valued at purchase or acquisition cost, or at market prices on the inventory date if those are lower. The definition of purchase price subtracts VAT that is deductible. Do not automatically assume that every business should use net amounts, or that a selling price is the right value.

Separate production-cost rules apply to self-manufactured goods and unfinished work. The regulation also requires reductions in inventory value for specified cost adjustments, including in cash-basis PIT cases. Flag such items for individual review instead of applying a single conversion rule to the whole table.

Check stock owned by the business but held elsewhere as well. Goods belonging to someone else and held at your premises are recorded by quantity with their owner identified, without valuation. Mixing owned and third-party stock is an error that accurate addition cannot fix.

What can AI check before you prepare PIT?

If you use an AI assistant to analyse tables, give it a defined task: compare the figures and identify entries that need explanation. A useful result includes line numbers and reasons for discrepancies, rather than only a final total.

1. Completeness: missing quantities, prices, units or document references should produce questions for review.
2. Arithmetic: compare quantity multiplied by price with each line value and the worksheet total.
3. Possible duplicates: similar names are not enough to delete an entry; they may represent different batches or storage locations.
4. Opening balance: check that the opening value matches the appropriate inventory closing the previous year.
5. Income effect: show the result before adjustment, the inventory difference and the adjusted result separately.

For example, you could use this instruction with a prepared table:

Check the arithmetic and completeness of this inventory table. Do not invent missing quantities or prices. List the item numbers needing clarification and explain why. Calculate the effect of the approved opening and closing inventory values on income, assuming that the supplied costs do not yet include this adjustment.

For example, a line contains 20 units at PLN 40 each, but its recorded value is PLN 80. Multiplication gives PLN 800. AI should flag the PLN 720 discrepancy and identify the item. It should not change the quantity to two just to make the table balance. The owner checks the count sheet and price record before approving a correction.

The AI output remains material for review. It does not prove that stock exists, belongs to the business or has been valued correctly. AI should not replace a missing price with an internet average or treat an empty field as zero. Recalculate after changes and keep the approved version.

How do you use verified values in Norman?

According to Norman’s annual PIT instructions, income is populated from the records and approved operations. For PIT-36 and PIT-36L, the user enters opening and closing inventory. A correct inventory value is therefore a specific input into tax preparation, not a figure to infer from bank history.

Before entering the values, check the accounting period and whether all relevant operations are included. Then compare the annual calculation with your own reconciliation of the inventory difference. If the figures differ, trace the cause to the records or treatment of costs; do not change the inventory to achieve an expected tax result.

The AI table checks described above are a suggested working method, not a claim that Norman automatically counts warehouse stock. The current product instructions describe preparing a return and downloading XML. You review and submit the return yourself; downloading a file does not mean a declaration was filed or tax was paid.

For the wider process, read how AI prepares taxes for a Polish sole trader. If you are also preparing electronic ledger data, see JPK_PKPIR timing and data preparation. Inventory helps determine income; reporting the ledger is a separate obligation.