Keeping correct accounting records is the foundation of every business. One of the most important questions that often raises doubts among business owners is whether expenses can be booked when they do not have a traditional invoice. It is worth stressing that an invoice is not the only document that allows expenses to be booked in the accounting books or in the KPiR (tax revenue and expense ledger).
Accounting entries can be based on various accounting documents (dowody księgowe), but their use is not entirely optional. The law specifies precisely which documents can form the basis for booking business transactions. Knowing these rules allows businesses to document all transactions correctly, which is essential for complying with tax and accounting law.
Accounting documents are the legal basis for all entries in the accounting books and in the KPiR. Preparing and storing them correctly is the duty of every business owner. Using the wrong documents can cause problems during a tax inspection
Types of accounting documents under the law
The catalogue of documents that can form the basis for entries in the KPiR is set out precisely in the regulation on keeping the tax revenue and expense ledger (from 1 January 2026, the regulation of the Minister of Finance and Economy of 6 September 2025, Journal of Laws (Dz.U.) 2025 item 1299). Under § 6 section 3 of this regulation, entries in the ledger are based on accounting documents, which can be divided into several main categories. In the accounting books (full accounting), entries are based on source documents – external documents received from others, external documents issued by the business and internal documents (Article 20 section 2 of the Accounting Act) – as well as aggregate, corrective, substitute and settlement documents (Article 20 section 3).
The first and most commonly used category is invoices, VAT RR invoices, bills and customs documents, which are collectively referred to as invoices. These documents must be issued in accordance with separate regulations, which means they must meet all the formal requirements of the VAT Act and other legislation governing invoicing.
Invoices are the most commonly used type of accounting document in business. They must meet all the formal requirements set out in tax law, including mandatory details such as the identification data of the parties, the subject of the sale and the VAT amounts
The second category is documents recording a reduction of tax-deductible costs or an increase in revenue under Article 22p of the PIT Act. These special documents must contain strictly defined details that ensure their reliability and allow the tax authorities to check them.
The third, very broad category is other documents listed in § 7 and § 8 of the regulation. These documents must confirm that the business transaction took place as it actually happened and contain all the details needed to document the transaction properly.
Formal requirements for accounting documents
Every accounting document, whatever its type, must meet certain formal requirements that ensure its reliability and usefulness for accounting and tax purposes. These requirements are set out in detail in the law (§ 6 section 3 point 3 of the KPiR regulation, Article 21 section 1 of the Accounting Act), and failing to meet them can cause problems during a tax inspection. When the paperwork piles up, you can hand it over to us – as part of our bookkeeping services, we post documents to the KPiR or the full accounting books.
The basic requirement is a reliable identification of the issuer or the parties involved in the business transaction. This means giving the full names and addresses of all entities involved in the transaction, which allows the participants to be identified unambiguously.
An accounting document should reliably identify the issuer or the parties to the transaction, that is the company names or the first names and surnames of individuals, together with their addresses (§ 6 section 3 point 3 letter a of the KPiR regulation, Article 21 section 1 point 2 of the Accounting Act). Missing information can lead the tax authorities to challenge the document during an inspection
Another key element is correct dating of the document. The document must contain the date of issue and the date or period of the business transaction it relates to. Where the transaction date is the same as the date of issue, one date is enough, which simplifies documentation.
The subject of the business transaction must also be described in detail, together with its value. If the subject of the transaction can be measured in natural units, its quantity must also be stated, which allows the transaction to be checked fully.
Documents must also bear the signatures of persons authorised to document business transactions properly. In addition, each document should be numbered or marked in another way that links it to the accounting entries made on its basis. In the accounting books, the document also states its type and number and includes the posting instruction (dekretacja) – an indication of the month and the way it is recorded in the books, signed by the person responsible (Article 21 section 1 points 1 and 6) – and signatures may in some cases be omitted or replaced with marks (Article 21 sections 1a and 4). How a document moves through the business from receipt to archive is shown in our article on the flow and storage of accounting documents.
Detailed catalogue of accounting documents
§ 7 of the KPiR regulation lists precisely the specific types of documents that can serve as accounting documents. Knowing this catalogue is essential for keeping correct records and avoiding problems during a tax inspection.
The regulation in force until 2025 also listed in this catalogue daily summaries of documents (sales invoices) prepared in order to book them with a single aggregate entry; the 2025 regulation no longer lists them. In the accounting books, aggregate entries are made using aggregate documents (Article 20 section 3 point 1 of the Accounting Act), which is particularly useful for businesses carrying out a large number of similar transactions.
An aggregate document allows a large number of similar transactions to be booked with one combined entry. The source documents must be listed individually in it (Article 20 section 3 point 1 of the Accounting Act)
The first type listed in § 7 is accounting notes, which are prepared to correct an entry concerning a business transaction resulting from an external or own document. These notes may be received from contractors or sent to them and are used to correct entries already made.
The former catalogue also included transfer documents, which record internal movements of funds or assets within the business; the 2025 regulation no longer lists them separately, and in the accounting books such transactions are documented with internal documents (Article 20 section 2 point 3 of the Accounting Act). Although these transactions do not involve outside parties, they still need to be documented properly for accounting purposes.
Another important category is postal and bank fee documents (§ 7 point 2), which record costs related to running the business. Today, when most transactions go through banks, these documents make up a large part of a business's accounting records.
Receipts as accounting documents – limits and options
Using receipts (paragon) as accounting documents is one of the topics businesses raise most often. Although the rules allow expenses to be booked on the basis of receipts, this option is limited to situations strictly defined by law.
Until the end of 2025, purchases of materials, cleaning and health and safety products and office supplies in retail outlets could be documented with a fiscal receipt (§ 13 section 4 of the 2019 regulation). This category of expenses covered the basic needs of every business, such as paper, pens or cleaning products. The regulation in force from 1 January 2026 does not provide for this exception.
From 1 January 2026, purchases of office supplies, cleaning products and health and safety products are not documented in the KPiR with a receipt alone without a NIP (tax identification number) – an invoice is needed. A receipt showing the buyer's NIP for up to PLN 450 is a simplified invoice (Article 106e section 5 point 3 of the VAT Act); for sellers covered by KSeF (National e-Invoicing System) – until 31 December 2026 (Article 145n)
A category of expenses that can still be documented with receipts is expenditure incurred abroad on fuel or oils (§ 8 section 4 of the KPiR regulation). This solution is particularly useful for businesses in the transport sector or those that often travel abroad on business.
A fiscal receipt or cash document for fuel bought abroad should contain the date, the identification of the issuer, the quantity, the unit price and the value of the purchase, and on the back you enter the first name and surname of the business owner (company name), the address and the type of purchase (§ 8 section 4). The full value of the receipt is booked in the tax revenue and expense ledger, but an important limitation is that the foreign tax on such expenses cannot be deducted in the Polish VAT return.
The exception is motorway toll receipts, which can be treated as invoices if they contain certain details. Under § 3 point 4 of the Minister of Finance regulation on issuing invoices (Journal of Laws 2021 item 1979, as amended), a motorway receipt (a single ticket for travel on a toll motorway) can be accepted as an accounting document if it meets detailed formal requirements.
Requirements for motorway toll receipts
Motorway toll receipts are a special category of accounting documents that can be treated in the same way as invoices if they meet certain formal requirements. This rule was introduced in response to the needs of businesses that often use motorways in the course of their activity.
For a motorway receipt to be accepted as a valid accounting document, it must contain the number and date of issue, which allows the document to be identified unambiguously and linked to a specific business transaction. It must also state the first name and surname or name of the taxpayer selling the service, that is the motorway operator.
Motorway receipts can be treated as invoices if they meet the detailed formal requirements set out in the rules. They must contain all the details needed to identify the transaction and allow the buyer of the service to deduct VAT
Another important element is the number under which the seller is identified for tax purposes, which usually means the NIP or another tax identifier. The receipt must also contain information identifying the type of service, in particular the name of the motorway for which the toll is charged.
The financial details of the receipt are also essential, namely the VAT amount and the total amount due. This information is necessary for the business using the motorway to account for VAT correctly.
Meeting all these requirements means that motorway receipts are treated as invoices, which also allows taxpayers to deduct VAT on the expense. This is a significant benefit for businesses, which can fully settle the costs of motorway travel.
Simplified invoices as accounting documents
Simplified invoices are a special category of accounting documents that can be issued in certain situations when the value of the transaction does not exceed specific thresholds. Under Article 106e section 5 of the VAT Act, a simplified invoice can be issued when the total amount due for the transaction does not exceed PLN 450 or EUR 100, if the amount is expressed in euro.
The main advantage of a simplified invoice is that some details mandatory on standard invoices can be left out. Businesses do not have to include the first name and surname or name of the buyer of the goods or services or the buyer's address on such invoices, which greatly simplifies issuing documents for small transactions.
Simplified invoices can be issued for transactions worth no more than PLN 450 or EUR 100. They do not require the buyer's details other than the NIP, which greatly simplifies documenting small sales, especially in retail
In addition, simplified invoices do not require the unit of measure and quantity of goods supplied or the scope of services performed, which also speeds up their preparation. You can also leave out the unit price of the goods or service excluding tax, that is the net price, and the value of goods supplied or services performed excluding tax.
Simplified invoices also do not have to contain information on VAT rates or the total net sales value broken down by sales subject to each tax rate and tax-exempt sales. You can also leave out the tax amounts on the total net sales value broken down by each tax rate.
The most important element of a simplified invoice, however, is the tax identification number, that is the buyer's NIP (Article 106e section 6), together with data allowing the tax amount to be determined for each rate (Article 106e section 5 point 3). These elements are necessary for VAT to be settled correctly and must appear on every simplified invoice.
Procedure for booking documents correctly
Booking accounting documents requires a set procedure that helps keep the accounting records correct and complete. The first step is always a formal check of the document, which involves verifying that it contains all the details required by law.
The check should cover the identification data of the parties, correct dating, a complete description of the subject of the transaction and the required signatures. Pay particular attention to whether the data matches how the transaction actually took place.
- Checking that the document is complete and formally correct
- Verifying that the data matches the actual course of the transaction
- Classifying the transaction and choosing the right accounts
- Preparing the accounting entry with an appropriate description
- Entering the record in the right accounting registers
- Archiving the document as required by law
After a positive formal check, the transaction is classified and the right accounts are chosen. This stage requires good knowledge of the chart of accounts and the rules for classifying transactions in line with the applicable accounting standards.
Correct classification of business transactions and choice of accounts are essential for reliable financial statements. Errors here can lead to an incorrect presentation of the company's financial position
The next step is preparing the accounting entry, which must contain all the information needed to identify the transaction and link it to the source document. The entry should have a description that clearly states the nature of the transaction.
Entries must be made in the right accounting registers in chronological order, keeping numbering continuous and meeting the deadlines set by law. The final stage is archiving the document as required by law, ensuring it is available throughout the storage period.
Storage periods for accounting documents
The obligation to store accounting documents is one of the fundamental requirements of tax and accounting law. Under the tax rules, accounting documents must be kept until the tax liability becomes time-barred, as a rule for 5 years, counted from the end of the calendar year in which the tax payment deadline passed (Article 86 § 1 and Article 70 § 1 of the Tax Ordinance Act (Ordynacja podatkowa)). The Accounting Act requires accounting documents to be kept for at least 5 years from the beginning of the year following the financial year they relate to (Article 74 section 2 point 8 and section 3) – for tax purposes they usually have to be kept longer. An entity does not have to archive invoices stored in KSeF itself for as long as they are stored in the system (Article 73a of the Accounting Act).
In practice, this rule means that invoices recorded in the KPiR in 2025 must be kept until the end of 2031, that is for 5 years from the end of 2026, the year in which the income tax payment deadline for 2025 passed. This approach simplifies document management, because you usually do not have to calculate the end of the storage period for each document separately.
For tax purposes, the storage period for accounting documents is, as a rule, 5 years from the end of the calendar year in which the tax payment deadline passed. Documents from a given tax year usually have the same storage period, which simplifies managing the archive; however, the limitation period may be suspended or interrupted (Article 70 § 2–6 of the Tax Ordinance Act)
For income tax, the storage period is counted from the tax payment deadline, which is set by the final deadline for filing the annual PIT return. This approach reduces the need to calculate deadlines individually for each document and return, which greatly simplifies managing accounting documentation.
The document archive should be organised chronologically by date. It is recommended to arrange documents from the oldest, at the very bottom, to the newest, on top of the whole set. Organising documents this way makes it easier to find specific documents and streamlines inspections.
It is worth stressing that failing to comply with the obligation to store accounting documents can have serious legal and financial consequences. The tax authorities have the right to inspect the accounting documentation throughout its mandatory storage period.
Consequences of documenting transactions incorrectly
Documenting business transactions incorrectly can lead to a number of negative consequences affecting various aspects of the business. The most important are the tax consequences, which may include tax-deductible costs being challenged, a higher tax liability being assessed, late-payment interest and liability under the Fiscal Penal Code.
During an inspection, the tax authorities analyse accounting documents in detail to check that they comply with the law. Documents that do not meet the formal requirements may be challenged, which means the related costs are excluded from tax-deductible costs. This increases the tax base and means additional tax has to be paid.
If the tax authorities challenge accounting documents, costs may be excluded from tax-deductible costs and the tax base increased. In addition, late-payment interest is charged, and keeping a ledger unreliably is punishable by a fine of up to 240 daily rates, or in less serious cases a fine for a fiscal petty offence (Article 61 of the Fiscal Penal Code)
The consequences may also include problems with deducting input VAT. Invoices that do not meet the formal requirements do not give the right to deduct VAT, which increases the real cost of purchasing goods or services. Where large amounts are involved, this can significantly affect the company's liquidity.
Incorrect documentation can also cause problems during inspections by other authorities, such as ZUS (Social Insurance Institution) or PIP (National Labour Inspectorate). Missing documentation can make it harder to show that social insurance contributions were settled correctly or that labour law was observed.
| Type of consequence | Area affected | Possible financial effects | How to avoid it |
|---|---|---|---|
| Tax | Tax-deductible costs | Additional tax, interest | Correct documentation |
| VAT | Input VAT deduction | No right to deduct | Invoices compliant with the rules |
| Contributions | Settlements with ZUS | Additional contributions | Complete documentation |
| Legal | External inspections | Administrative penalties | Compliance with the rules |
Most common errors in documenting business transactions
An analysis of business practice points to several errors made most often when documenting business transactions. Knowing these errors helps you avoid them and keep your accounting records correct.
The first of the most common errors is incomplete or incorrect identification data of the parties to the transaction. Business owners sometimes leave out parts of the address, give incomplete company names or wrong tax identification numbers. Errors like these can lead the tax authorities to challenge the document.
Another common problem is incorrect dating of documents. Situations where the date of issue does not match the date of the transaction and the business does not give both dates as the rules require are particularly problematic. This can cause problems with correctly determining when the tax obligation arose.
The most common errors in documenting business transactions are incomplete identification data of the parties, incorrect dating and an insufficient description of the subject of the transaction. Each of these errors can lead the inspection authorities to challenge the document
Another significant problem is an insufficient description of the subject of the transaction. Overly general terms such as "services" or "goods" do not meet the requirements of the rules, which call for a precise description of the subject of the transaction. The description should be detailed enough to identify unambiguously what the transaction concerned.
Errors also concern procedural matters, such as missing signatures of persons authorised to document business transactions or incorrect numbering of documents. These seemingly minor shortcomings can have significant consequences during a tax inspection.
- Incomplete or incorrect identification data of contractors
- Incorrect dating of accounting documents
- Insufficient description of the subject of the transaction
- Missing signatures of authorised persons
- Incorrect numbering and archiving of documents
- Using the wrong types of accounting documents
Digitising accounting documents
Modern technology gives businesses the option of digitising accounting processes, including storing accounting documents electronically. The law allows accounting documentation to be kept electronically, provided certain technical and organisational requirements are met.
Digitising accounting documents can bring significant benefits, such as saving archive space, making documents easier to find and increasing storage security. However, implementing an electronic system requires the integrity and authenticity of documents to be ensured throughout their mandatory storage period.
Accounting documents may be stored electronically, provided their integrity, authenticity and legibility are ensured throughout the mandatory storage period. The system must allow documents to be reproduced in a form legible to the inspection authorities
The key requirement is to ensure that electronic accounting documents remain legible and available throughout the storage period. This means making regular backups, updating IT systems and ensuring that file formats remain compatible with future technologies.
The electronic system must also make it possible to establish the source of entries and the person responsible for entering them (Article 20 section 5 point 2 of the Accounting Act); erasing and altering the documents themselves is not permitted (Article 22 section 1). These functions are necessary to keep the accounting documentation reliable and to meet the requirements of the inspection authorities.
A medium-sized manufacturing company that decided to fully digitise its accounting documentation reduced the time spent searching for documents and cut its archiving costs. The electronic system also gave it better control over document flow and allowed it to close the accounting month faster.
