Correct numbering of accounting documents is the foundation of a reliably kept KPiR (tax revenue and expense ledger). Many business owners struggle with choosing the right numbering system, which can lead to problems with the tax authorities. Marking accounting documents properly not only keeps you compliant with the rules but also makes it easier to check and manage your company's records.
Numbering accounting documents is more than just putting papers in order. It is part of the internal control system that lets you identify each business transaction unambiguously and keeps the records continuous. Incorrect numbering can lead not only to sanctions from the tax office (urząd skarbowy) but can also make day-to-day running of the business harder.
Legal basis for numbering accounting documents
The obligation to number accounting documents correctly comes from specific tax provisions. From 1 January 2026, the way this ledger is kept and the requirements for accounting documents are set out in detail in the regulation of the Minister of Finance and Economy of 6 September 2025 on keeping the tax revenue and expense ledger (Journal of Laws (Dz.U.) 2025 item 1299), which replaced the regulation of 23 December 2019. When a bank transfer confirmation alone can serve as the document is explained in a separate article.
Under § 5 of the regulation, a taxpayer who keeps the ledger without computer software must bind the ledger and number its pages consecutively. Entries in the ledger receive a consecutive sequence number, and the accounting document should be marked with a number or in another way that links it to the entry made on its basis (§ 6(3))
According to the explanatory notes to the ledger template, the first column of the tax revenue and expense ledger is for the sequence number of entries in the ledger. Until the end of 2025, the notes expressly required the document on which the entry was based to be marked with the same number. From 2026, a marking that links the document to the entry is enough, and column 3 is for the invoice number assigned in KSeF (National e-Invoicing System) (column 4 is for any other document number). Marking the document with the entry's sequence number is still the simplest way to keep source documents and ledger entries consistent. Warehouse documents raise questions of their own – for example, recording WZ notes in the KPiR.
Article 88 of the Tax Ordinance Act (Ordynacja podatkowa) also sets out obligations for numbering bills (rachunki). Taxpayers who issue bills must number them consecutively and keep copies in the order of issue until the tax liability becomes time-barred.
Tax provisions do not contain detailed instructions on how to number accounting documents. This gives business owners freedom to choose a method, but it also requires them to follow the basic principles of chronological order and continuous numbering
Because the law does not regulate the details of numbering precisely, misunderstandings with the tax authorities can arise. That is why it is so important to understand the general principles and apply them consistently in practice.
Numbering methods used in practice
In practice, business owners mainly use two methods of numbering accounting documents. Each has its advantages and may suit different business situations.
Annual numbering
Annual numbering is the method taxpayers choose most often. Numbering starts from 1 at the beginning of the tax year or when the business starts, and consecutive numbers continue until the end of the tax year.
With annual numbering, the first document of the year gets number 1, the second number 2, and so on until the end of the tax year or until the business closes. This system keeps the records clear and easy to check throughout the financial year.
Annual numbering starts on 1 January of each tax year or on the day the business starts. Subsequent documents receive numbers in chronological order until the end of the year or until the business closes. This system keeps numbering continuous throughout the financial year
Monthly numbering
The alternative to annual numbering is monthly numbering. Here, numbering starts again every month, which can be practical for companies with a large number of accounting documents or a specific way of organising their accounting.
Monthly numbering requires extra care when marking documents, to avoid confusion caused by the same numbers recurring in different months. An additional month or year marker is often used.
Rules for correct numbering
Whichever numbering method you choose, there are basic rules to follow when marking accounting documents. They follow from the requirement that the records are reliable and unambiguous.
- Keep the numbering in the chronological order in which documents arise
- Keep the numbering continuous without skipping numbers
- Avoid repeated numbers within the chosen system
- Apply the chosen method consistently throughout the settlement period
- Mark documents in a way that allows unambiguous identification
The ledger should allow the business events recorded in it to be identified unambiguously, which shows that it is reliable. Items must be numbered in sequence so that numbers do not repeat - there cannot be more than one item with the same number
The basic rule is to keep documents in chronological order. Documents created earlier should receive lower numbers than documents created later. This order makes it easier to check and analyse business transactions.
Continuous numbering means you cannot skip numbers in the sequence. If the last document received number 150, the next one must receive number 151. Gaps in numbering may make inspectors suspect that the records are incomplete.
Practical aspects of introducing numbering
Introducing a numbering system for accounting documents requires well-thought-out organisation of accounting processes in the company. The key is to decide when documents receive their numbers and how they are recorded.
The moment a document receives its number should be clearly defined and applied consistently. Most often the number is assigned when the document is entered into the records, not when it is created or received.
| Process stage | Activity | Responsibility | Check |
|---|---|---|---|
| Receiving the document | Formal verification | Accounting department | Completeness check |
| Assigning a number | Marking with the next number | Accountant | Continuity check |
| Entering in the KPiR | Entry in the ledger | Accountant | Consistency check |
| Archiving | Storing the document | Accounting department | Access control |
It is also important to set out what to do in exceptional situations, such as numbering mistakes, documents received late or corrections to entries made earlier.
Taxpayers often decide themselves how to record company documents. Remember, however, that the ledger should allow the business events recorded in it to be identified unambiguously, which shows that it is reliable
Rulings of the tax authorities
Doubts about numbering accounting documents are often the subject of tax rulings. A particularly useful pointer is an individual tax ruling (interpretacja indywidualna) issued by the Director of the Tax Chamber in Poznań on behalf of the Minister of Finance.
In the ruling of 5 August 2011, ref. ILPB1/415-676/11-2/AG (issued under the 2003 regulation), the tax authority stated that the numbering of accounting documents should be continued throughout the year. Any change to the numbering method is best made at the start of a new tax year.
The Director of the Tax Chamber in Poznań stated in an individual tax ruling that the numbering of accounting documents should be continued throughout the year, and any change to the numbering method is best made at the start of a new tax year
This ruling confirms that the tax authorities expect the chosen numbering system to be applied consistently. Changes during the year can make it harder to check the records and to link documents to ledger entries.
The ruling also highlights the importance of planning the numbering system at the beginning of the tax year. A well-thought-out approach helps you avoid problems later and meets the expectations of inspectors.
The most common numbering mistakes
Practice shows that business owners make typical mistakes when numbering accounting documents. Knowing these pitfalls helps you avoid them and keep your records in line with the rules.
The most common mistakes are:
- Skipping numbers in the sequence
- Repeating numbers for different documents
- Changing the numbering system during the tax year
- Numbering documents out of the chronological order in which they were entered in the records
- Inconsistency between numbers in the KPiR and numbers on the source documents
The rules do not regulate the exact form of numbering, which gives you freedom, but on the other hand it sometimes causes inaccuracies that lead to disputes with the tax office
Skipping numbers in the sequence is one of the most serious mistakes, because it may suggest that business transactions are being hidden. Inspectors check the continuity of numbering very carefully, and every gap needs an explanation.
Repeating numbers causes chaos in the records and makes it impossible to identify documents unambiguously. Such a mistake may mean reorganising the whole numbering, which is time-consuming and costly.
Electronic systems and numbering
Modern accounting systems make correct numbering of accounting documents much easier. Automating this process reduces the risk of human error and makes it easier to stay compliant with the rules.
Electronic systems offer various functions that support numbering:
- Automatic assignment of consecutive numbers
- Numbering continuity checks
- Choice of numbering system (annual/monthly)
- Protection against repeated numbers
- Generating control reports
Modern accounting systems number documents automatically in chronological order, which reduces the risk of numbering mistakes. The user can define the numbering method at the beginning of the year, and the system will apply the chosen rules consistently throughout the settlement period.
Automatic numbering does not, however, remove the need to check and supervise the process. Accountants still have to verify that the numbering is correct and react to any irregularities.
The numbering system in accounting software should be configured by someone with the right knowledge and experience. Incorrect settings can cause problems for the whole financial year.
Checking and verifying the numbering
Regular checks of the numbering of accounting documents are essential to keep the records reliable. Checks should cover different aspects of the numbering and be carried out systematically.
What to check:
- Continuity of numbering in given periods
- Consistency of numbers in the KPiR with the numbers on documents
- Chronological order of assigned numbers
- Any gaps in the numbering
- Correct markings where monthly numbering is used
Numbering should be checked regularly, ideally at the end of each month. This lets you spot and correct any mistakes quickly before they pile up. Pay particular attention to the turn of settlement periods
Records of numbering checks should be kept as part of the internal control system. During an external inspection, such records can help show that the records have been kept reliably.
Control procedures should be adapted to the nature of the business and the size of the company. Small businesses can use simpler checks, while larger companies need more advanced systems.
Archiving and storage
Properly numbered accounting documents must be archived and stored in line with the law. Numbering makes it easier to organise the archive and find documents quickly.
Rules for archiving numbered documents:
- Storing documents in numerical or chronological order
- Protecting them against loss or damage
- Ensuring access for inspection authorities
- Keeping a register of stored documents
- Observing storage periods
Accounting documents on which KPiR entries were based are marked with a number or in another way that links them to the ledger entry – in practice most often with the sequence number of that entry. Documents must be stored in a way that allows them to be found and verified quickly
The archiving system should take account of the numbering used. With monthly numbering, an additional month or year marker may be needed to make sorting easier.
Electronic archiving systems offer extra options, such as searching by document number or generating indexes automatically. Remember, however, that electronic data must be protected.
Summary of the key rules
Correct numbering of accounting documents in the KPiR requires you to follow a few basic rules. Taxpayers are free to choose between annual and monthly numbering, but they must apply the chosen method consistently. Our accounting firm in Warsaw keeps the KPiR for business owners, document numbering included.
The key rules are chronological order, continuous numbering and unambiguous marking of documents. Changes to the numbering system should be introduced at the start of a new tax year, in line with the tax authorities' rulings.
Modern accounting systems make correct numbering much easier, but they do not replace checking and supervising the process. Regular verification of the numbering and proper archiving of documents are just as important as the numbering itself.
