KPiR is the primary tax record for many small businesses. We explain how to maintain it correctly, which columns to fill in and what mistakes to avoid in 2026.
The revenue and expense ledger, abbreviated as KPiR, is the most commonly chosen form of tax record-keeping by sole traders and partnerships taxed under general rules or a flat income tax rate. Despite its apparent simplicity, KPiR is governed by strict rules – errors in entries can result in tax penalties or the need to correct an annual tax return. In this guide we explain who is required to maintain KPiR, how to correctly complete each column, which documents serve as the basis for entries, and what to pay particular attention to in order to avoid the most common mistakes.
The obligation to maintain the revenue and expense ledger applies to individuals conducting business activity, civil partnerships and general partnerships of individuals, and professional partnerships that pay income tax under general rules (tax scale) or a flat income tax rate. KPiR is not, however, the appropriate form of record-keeping for taxpayers covered by the lump-sum tax on recorded revenue – those taxpayers maintain a separate revenue register. It is worth noting that from 2026 the JPK_PKPIR obligation also applies, i.e. the electronic structure of the Jednolity Plik Kontrolny (Standard Audit File) for the revenue and expense ledger. This means that KPiR data must be stored and, upon request of the tax authority, submitted in a specified XML format – which places new requirements on entrepreneurs maintaining records manually or using outdated software.
The revenue and expense ledger consists of 17 columns, each used to record a different type of economic event. The most important ones are as follows: • Column 1 – sequential entry number. • Column 2 – date of the economic event. • Column 3 – accounting document number (e.g. invoice number). • Columns 4 and 5 – counterparty details (name and address). • Column 7 – revenue from the sale of goods and services. • Column 8 – other revenue (e.g. interest, compensation). • Column 10 – purchase of trading goods and primary materials. • Column 11 – ancillary purchase costs (transport, packaging). • Column 13 – other expenses (wages, rent, services). • Columns 16 and 17 – remarks and additional notes. Correctly assigning a cost to the appropriate column has a direct impact on the calculation of income and the tax base.
Every entry in KPiR must be supported by an appropriate accounting document. The catalogue of accepted documents is broad, but not unlimited. The primary documents include: • VAT invoices and simplified invoices – the most commonly used document for purchases and sales. • Receipts issued by entities not required to issue invoices. • Accounting notes – used, among other things, for mutual settlement adjustments. • Customs documents – for imports of goods from outside the EU. • Internal documents – for expenditure that cannot be documented by an invoice (e.g. purchases at a market, parking fees documented by a receipt without NIP). • Payroll records – as proof of wage payments. From 2026, in connection with the implementation of mandatory KSeF, structured invoices are becoming the standard. Their KSeF number should be noted in the records, which facilitates any potential audit.
The rules governing the moment at which an event is recognised in KPiR are precisely regulated. Revenue must be recorded on an ongoing basis – on the date the invoice is issued or the service is performed, whichever occurs first. Deductible costs are subject to two accounting methods: 1. Cash method – the cost is recognised on the date of actual payment. 2. Accrual method – the cost is recognised on the date the invoice is issued or received. The chosen method must be applied consistently throughout the entire tax year. Entries should be made no later than on the day the advance tax declaration is filed or – for quarterly advance payments – by the 20th day of the month following the end of the quarter. In practice, it is recommended to make entries on an ongoing basis, which minimises the risk of omitting documents and facilitates the preparation of JPK_PKPIR.
Even experienced entrepreneurs make mistakes in KPiR that can prove costly during a tax audit. The following are those that occur most frequently: • Recording a cost in the wrong column – e.g. entering a transport service in column 13 instead of column 11. • Absence of an accounting document for an expense – entering a cost without an invoice or other accepted document. • Late recording of revenue – which may lead to an understatement of advance income tax payments. • Including expenditure that does not constitute deductible costs – e.g. contractual penalties resulting from the taxpayer's own negligence. • Incorrect conversion of foreign currency invoices – conversions must use the NBP exchange rate from the day preceding the date the document was issued. • Lack of synchronisation between KPiR and the VAT register – discrepancies between the two records are one of the first warning signals for tax authorities.
The year 2026 brings a significant change for all taxpayers maintaining KPiR. The obligation to submit the Standard Audit File in the JPK_PKPIR structure means that the ledger must be maintained in electronic form, compliant with the requirements of the Ministry of Finance. JPK_PKPIR files contain detailed data on every entry – including the document number, counterparty details, amounts in the relevant columns and the date of the event. Maintaining KPiR in a spreadsheet without the appropriate structure will not meet these requirements. It is recommended to use accounting software certified by its developer as compliant with the JPK format, or to commission the maintenance of the ledger to a professional accounting firm that has the appropriate tools and keeps them up to date.
Correctly maintaining the revenue and expense ledger requires knowledge of the regulations, consistency and appropriate tools – particularly following the introduction of JPK_PKPIR and mandatory KSeF in 2026. If you want to be certain that your records are maintained in accordance with the applicable regulations, contact the Danexis accounting firm from Wrocław. Call +48 780 760 666 or write to kontakt@danexis.pl – we will be happy to discuss your situation and propose an optimal solution.