Accounting documents: requirements, flow and storage

Accounting documents are the fundamental basis of the entire accounting system in every business entity. Without properly prepared and documented accounting documents, it is impossible to keep reliable accounting records or prepare credible financial statements. Every document that is to be recognised as an accounting document must meet strictly defined legal requirements regarding both content and form.

A well-functioning system of accounting documents requires not only knowledge of the law but also an understanding of how it is applied in day-to-day business. Modern companies have to deal with a growing number of documents that need proper processing, checking and archiving.

Types of accounting documents

The system of accounting documents covers various categories of documents that can be divided into several basic groups. Each group has a specific function in documenting business transactions and needs to be handled accordingly.

External documents received are documents obtained from outside business partners, such as purchase invoices, bills, transport documents or payment confirmations. They confirm transactions with external parties and are the basis for recording the transaction in the entity's accounting books. VAT taxpayers are, as a rule, obliged to issue structured invoices in KSeF (National e-Invoicing System) (Article 106ga(1) of the VAT Act) – the accounting document is then the invoice with the number assigned in that system.

External documents issued include documents issued by the entity and given in the original to the business partner. They include sales invoices, bills issued to customers, goods issue documents or confirmations of services. Copies of these documents remain with the entity as the basis for entries.

Source documents are the original documentation of business transactions, while secondary documents are created by processing information contained in source documents. Secondary documents include summary, correcting, substitute and settlement documents. The Act distinguishes source documents – external received, external issued and internal – as well as documents prepared by the entity: summary, correcting, substitute and settlement documents (Article 20 sections 2–3). The head of the entity may allow a substitute document only where it is justifiably impossible to obtain the external document, and never for purchases subject to VAT (Article 20 section 4).

Formal requirements for accounting documents

Every accounting document must contain certain elements to be recognised as a valid accounting document. These requirements come directly from the Accounting Act and are meant to ensure that the accounting documentation is complete and credible.

The basic elements of an accounting document include the type of document and its identification number, which allows the document to be identified unambiguously in the records. This number should be unique and assigned according to the adopted numbering system.

1. Identification of the parties to the business transaction, with full names and addresses
2. A detailed description of the transaction, with its value in monetary and physical units
3. The date of the transaction and the date the document was prepared, if different
4. The signature of the issuer and of the person taking part in the transaction
5. Confirmation of the check and the account allocation of the document by the responsible person
6. Indication of the month and the method of recording in the accounting books

The description of the transaction should be complete and understandable; generally accepted abbreviations may be used. The value of the transaction should be stated in monetary units and, where possible, also in physical units.

The parties may be identified in different ways depending on the type of document. On external documents the parties may be indicated with a company stamp. If the document is an internal one, the organisational unit responsible for the transaction must be indicated.

The form of the accounting document – paper or electronic – does not affect the requirements for its content. The only difference is the medium on which the document is stored. A structured invoice received or issued in KSeF is also an accounting document. Entrepreneurs keeping a KPiR (tax revenue and expense ledger) apply their own catalogue of documents and their minimum content set out in the KPiR regulation (Journal of Laws (Dz.U.) 2025 item 1299, § 6 section 3, § 7 and § 8).

Exceptions to the formal requirements

The legislator provided for certain exceptions in Article 21 section 1a of the Accounting Act. The type and number of the document, the parties, the description and value of the transaction and the signatures may be omitted where separate regulations allow it. The confirmation that the document has been checked and qualified for entry in the accounting books may be omitted where this results from the technique used to document accounting entries.

Situations in which the exceptions apply:

• Separate regulations exempt you from including certain data on the document (Article 21 section 1a point 1)
• The technique of documenting entries, e.g. books kept on a computer, allows the account allocation to be omitted (Article 21 section 1a point 2)
• Signatures may be replaced with marks that identify the persons, where the document does not document the transfer or receipt of an asset or a transfer of ownership and is not a substitute document (Article 21 section 4)
• Entries made automatically or generated by an algorithm are treated as equivalent to source documents if they meet the conditions of Article 20 section 5 (including a permanently legible form and the possibility of identifying the source and the person responsible)

Functions of accounting documents

Accounting documents perform several important functions in the accounting system, which complement each other and support the management of the business. Understanding these functions is key to using accounting documentation properly.

The documentary function means recording information about a business transaction in a durable and verifiable way. An accounting document is written confirmation that a given business event took place at a particular time and place.

The evidential function confirms that the transactions shown in the document really took place at a given place and time. This function is particularly important during inspections carried out by external authorities.

The accounting function means that an accounting document is the basis for recording the transaction in the accounting books. Without a properly prepared accounting document, no entry can be made in the records.

The control function makes it possible to check whether transactions were correct and lawful. Thanks to this function, errors, irregularities or abuse in managing the business can be detected.

Rules for preparing accounting documents

Accounting documents should be issued carefully, legibly and durably. This means using suitable materials and tools that keep the record durable for the required storage period.

After preparing and signing the document, the issuer should promptly present it for signature to the person responsible for the business transaction and its documentation. This procedure ensures proper supervision of the documentation process.

Accounting documents should be reliable, i.e. consistent with the actual course of the business transaction. Reliability means not only correct figures but also that the description matches the actual nature of the transaction.

Accounting documents in a foreign currency

As business becomes more global, more and more companies carry out transactions in foreign currencies. Accounting documents denominated in foreign currencies require special treatment under the Accounting Act.

Rules for converting foreign currencies

1. Determining the exchange rate applicable to the transaction date – the rate actually applied when buying or selling currency and paying receivables or liabilities, and in other cases the average NBP (National Bank of Poland) rate from the previous day (Article 30 section 2 of the Accounting Act)
2. Converting the value of the transaction into Polish currency
3. Showing the result of the conversion on the accounting document
4. Documenting exchange differences where they arise
5. Archiving information on the exchange rate applied

The exchange rate used for the conversion must be the rate applicable on the day of the business transaction, not on the day the document was prepared (Article 21 section 3 of the Accounting Act). Where the computer system converts amounts automatically, the conversion method must be confirmed by a suitable system printout.

An importing company received an invoice from a German supplier for EUR 5,000. The transaction took place on 15 March 2025, and in this example the average NBP rate from the previous day was PLN 4.2850. The document must show the conversion: EUR 5,000 × 4.2850 = PLN 21,425.00. Payment was made on 30 March, when the rate actually applied by the bank was PLN 4.3100, resulting in a negative exchange difference of PLN 125.00.

Accounting documents in a foreign language

Accounting documents prepared in a foreign language are another challenge for those keeping the books. They occur in the public finance sector, but they also affect companies working with foreign business partners. At the request of the inspection authorities or the statutory auditor, the entity must provide a reliable translation into Polish of the content of the documents they indicate (Article 21 section 5 of the Accounting Act).

Authorities entitled to request translations include in particular:

• Regional Audit Chamber (Regionalna Izba Obrachunkowa)
• Supreme Audit Office (Najwyższa Izba Kontroli)
• KAS (National Revenue Administration) authorities (tax office, customs and tax office)
• European Court of Auditors
• Statutory auditor

Public institutions often translate documents issued in a foreign language that confirm foreign transactions on an ongoing basis, and usually set out the rules for doing so in internal procedures. This follows from the principle of transparency in public finances, which requires financial documentation to be fully legible.

Correcting errors in accounting documents

The law clearly sets out how to proceed when errors are found in accounting documents. Erasing and altering documents is not allowed, in order to preserve the integrity and credibility of the documentation.

Errors in external documents received and issued can only be corrected by sending the business partner a document containing the correction together with an appropriate justification, unless other provisions state otherwise (Article 22(2) of the Accounting Act) – for example, the VAT Act provides for corrective invoices (Article 106j). This procedure ensures that both parties to the transaction have consistent information about it.

Errors in internal documents may be corrected by crossing out the incorrect text or amount while keeping the crossed-out words or figures legible. The correct text, the date of the correction and the signature of the person authorised to make it must then be added. If the incorrect document has already been posted, the entry in the books itself is corrected under Article 25 of the Accounting Act.

• Crossing out the incorrect text must keep the original entry legible
• The correction must bear the date and signature of an authorised person
• Individual letters or digits cannot be corrected
• A correction of an external document requires an appropriate justification
• Corrections must not affect the integrity of the document

Checking accounting documents

A thorough check of accounting documents is a key element of the accounting system. It covers checking the lawfulness, reliability and correctness of the events and transactions reflected in the documents.

The substantive check consists of examining whether the data in the document correspond to reality, whether the transaction shown in the document was economically justified and whether it complies with the law.

The list of people authorised to carry out substantive checks should be tailored to the entity's needs and the types of business it conducts. It should be integrated with the organisational regulations and the document flow chart.

Practical example: A trading company received an invoice for consultancy services of PLN 50,000. During the substantive check, it was verified whether the service had actually been performed, whether it complied with the contract and whether the amount matched the agreed rates. It was also verified whether the expense was justified from the point of view of the company's business.

It is recommended to introduce the "four eyes" principle, i.e. having the document checked by two people, which minimises the risk of entering a defective document in the books. After completing the check, the checker should – in line with the rules adopted by the entity – place an appropriate clause on the document.

Account allocation of accounting documents

Account allocation (dekretacja) means indicating the month in which the document should be recorded in the accounting books and the accounts on which the transaction should be posted. This process is key to recording the transaction correctly in the accounting system.

Confirmation of the document's classification requires the signature of the person responsible for these indications. The person allocating the accounts must have the appropriate authority and accounting knowledge to indicate correctly how the transaction should be recorded.

There is no need to include allocation data if the accounting document is prepared on a computer and the data processing technique clearly indicates how such documents are posted. Modern accounting systems often automate account allocation.

1. Analysis of the nature of the business transaction
2. Determining the correct posting month
3. Indicating the accounts to be debited and credited
4. Checking consistency with the chart of accounts
5. Signing of the allocation by an authorised person

Account allocation in electronic systems

Traditionally, account allocation involves writing the month and the way the document is recorded in the accounting books, often using a posting stamp. The legislator allows you to dispense with manual account allocation where this results from the technique used to document accounting entries (Article 21 section 1a point 2). This mainly means using a computer system that records financial transactions automatically according to programmed algorithms.

In practice, an automatic posting system should provide:

• The ability to print the posting record
• Information on how the entry is recorded in the accounting books
• Data linking the printout to the document
• The ability to check that the posting is correct
• A function for making corrections when errors occur

Storing accounting documents

The Accounting Act requires accounting documents to be stored for specified periods – accounting documents as a rule for at least 5 years (Article 74(2)). Approved annual financial statements are stored for at least 5 years, counting from the beginning of the year following the financial year in which they were approved (Article 74(1)).

Storage periods for other records are counted from the beginning of the year following the financial year to which the records relate (Article 74(3)). The documentation must be stored properly and protected against unauthorised changes, unauthorised disclosure, damage or destruction.

Accounting documents and stocktaking documents are stored at the entity in their original form, in a fixed order suited to the way the accounting books are kept. Documents should be divided into reporting periods in a way that allows them to be found easily (Article 73(1)). This does not apply to invoices stored in KSeF (Article 73a) – the system stores them for 10 years from the end of the year in which they were issued (Article 112aa of the VAT Act). We list the document types and the deadlines that apply to them in our article on storage periods for accounting documents.

The content of documents may be transferred to electronic data media that preserve it in a permanent and unchanged form, provided it can be printed – except, among others, for documents transferring rights to real estate, entrusting responsibility for assets and significant contracts (Article 73 section 2). Documents concerning, among others, loans, credit facilities, commercial contracts and claims are kept for 5 years from the beginning of the year following the year in which the transactions were finally completed, settled or time-barred (Article 74 section 2 point 4).

The storage period for documents is directly linked to the moment the tax liability becomes time-barred. A tax liability becomes time-barred after 5 years, counting from the end of the calendar year in which the tax payment deadline passed (Article 70 § 1 of the Tax Ordinance Act (Ordynacja podatkowa)). Until then, the books and the documents relating to them must be kept for tax purposes (Article 86 § 1), even if the period under the Accounting Act has already expired. Posting documents and keeping the books for clients is the core of the work of our accounting office.

Pension and payroll documents

Special requirements apply to storing documents related to social insurance and pensions. The contribution payer must keep copies of settlement declarations, monthly personal reports and correcting documents for 5 years from the day they were submitted to ZUS (Social Insurance Institution) (Article 47(3c) of the Social Insurance System Act).

Payroll lists, pay cards and other documents on the basis of which the pension or disability pension assessment base is determined must, as a rule, be stored for 50 years from the day the insured person ended work for the given payer. For employees and contractors under a contract of mandate (umowa zlecenia) registered for insurance after 31 December 2018, or for whom a ZUS RIA information report has been submitted, this period is 10 years from the end of the year in which they ended work or the report was submitted (Article 125a(4)–(4b) of the Act on Pensions from the Social Insurance Fund (FUS)).

• Employee records - 10 years from the end of the year in which employment ended (Article 94 point 9b of the Labour Code (Kodeks pracy); transitional periods apply to earlier employment)
• Payroll records - 50 years from the end of work or 10 years (registration after 2018 or ZUS RIA)
• ZUS declarations - 5 years from submission
• Monthly reports - 5 years from submission
• Correcting documents - 5 years from submission

Instructions for the flow and control of accounting documents

Every entity should have documentation describing its adopted accounting policies, including instructions for the flow and control of accounting documents. These instructions should ensure that the information and control functions of the accounting system work properly.

The instructions for the flow and control of accounting documents affect the organisation of the entity's work, especially the finance and accounting departments and the units responsible for managing assets. The organisation of the accounting books is closely linked to the adopted rules for document flow and control.

Document flow depends on the entity's organisational structure and must be adapted to it. The route of documents and the control procedures depend on the internal structure of the entity, which must ensure proper document flow.

Example structure of the instructions: A medium-sized manufacturing company drew up document flow instructions covering 12 types of accounting documents. For each type, it set out who is responsible for issuing, substantive checking, formal and arithmetical checking and account allocation. The instructions also contained specimen signatures, stamps and forms used in the company.

Responsibility for accounting documents

Different people are responsible for preparing, checking and storing accounting documents, depending on the type of document and the organisational structure of the entity. This responsibility is both organisational and legal.

Division of responsibility:

• Head of the entity - ultimate responsibility for performing accounting duties, also where they have been entrusted to another person or an accounting office (Article 4 section 5)
• Chief accountant - the substantive side of the bookkeeping process
• Persons preparing documents - reliability and completeness of documents
• Persons checking documents - proper verification before posting
• All employees - following procedures and reporting irregularities

Electronic systems and data protection

Keeping accounting books on a computer requires special safeguards and procedures. Entries made automatically via communication devices or computer data carriers are regarded as equivalent to source documents.

Electronic entries must take a permanently legible form consistent with the content of the relevant accounting documents. It must be possible to establish their source and the person responsible for entering them.

The procedure used must ensure that the correct processing of data and the completeness and identity of entries can be checked. Source data at the place where they are created must be properly protected for the period required for storing the documents.

1. Using data carriers resistant to threats
2. Choosing suitable external protection measures
3. Systematically making backup copies of data sets
4. Protecting software and data against unauthorised access
5. Checking the continuity of entries and the carrying forward of balances

Frequently asked questions