How to issue an invoice correctly in 2026 – the mandatory elements

An invoice is the settlement document from which the whole tax machine starts – VAT, PIT/CIT, JPK (the Standard Audit File). In 2026 in Poland, invoices between VAT payers are issued in KSeF (the national e-invoicing system) – from 1 February for large taxpayers, from 1 April for the others; transitional exceptions apply until 31 December 2026. This is a revolutionary change technically, but the mandatory elements of the invoice itself have mostly stayed the same – they come from Article 106e of the VAT Act.

This article explains what must appear on a correct invoice, what the most common mistakes are, and how issuing through KSeF differs from the classic method. The guide reflects the legal position as at October 2026.

The mandatory elements of an invoice (Article 106e)

The VAT Act (Article 106e(1)) lists the elements an invoice should contain. After the change from 1 February 2026 the provision has points 1–27 (points 26–27 apply from 1 February 2026). The most important are:

• The date of issue and the sequential number of the invoice, given within a series
• First names and surnames or names and addresses of the seller and the buyer
• The seller’s NIP (tax identification number) and the buyer’s NIP (or EU VAT number)
• The date of delivery of the goods or performance of the service (if different from the date of issue)
• The name (type) of the goods or service, the unit of measure and quantity
• The net unit price, amounts of discounts or reductions, the net value for the line
• The VAT rate, the total of net values by rate, the amount of VAT, the total amount due
• Special markings – among others the split payment mechanism (MPP), reverse charge, the margin scheme
• The basis for the VAT exemption (Article 106e(1) point 19) – key for taxpayers exempt from VAT

A signature and a stamp are not mandatory elements of an invoice. In practice invoicing programs fill in most of these fields automatically. KSeF enforces the FA(3) structure (the binding template of the invoice file), which reflects the requirements of Article 106e.

Date of issue vs date of sale – the most common misunderstanding

These two dates are different in concept and have different effects.

The date of issue

This is the day the invoice was created (in the program, in KSeF, on paper before 2026). It determines the deadline for issuing – Article 106i(1) of the VAT Act:

An invoice is issued no later than on the 15th day of the month following the month in which the goods were delivered or the service performed.

The date of sale (delivery / performance of the service)

This is the day on which the delivery or performance took place. The key date for VAT – the moment the tax obligation arises (Article 19a of the VAT Act).

Example

You sell a consulting service on 28 March 2026. The invoice is issued on 12 April 2026.

• Date of sale: 28 March 2026 → VAT for March (the JPK_V7 return for March, due 25 April)
• Date of issue: 12 April 2026 → the date the document appeared

A common mistake: putting the date of issue in the “date of sale” field – this shifts VAT forward by a month, which is incorrect.

NIP – who has to give it and when

• The seller – always their own NIP (Article 106e(1) point 5)
• The buyer – a NIP or EU VAT number (Article 106e(1) point 6), with exceptions:

No obligation to give the buyer’s NIP:

• An invoice for a consumer (B2C without a NIP)
• An invoice for a motorway toll, a rail ticket, an air ticket

A simplified invoice up to PLN 450 gross is the opposite case: it contains the buyer’s NIP instead of their name and address (Article 106e(5) point 3).

In KSeF (from 1 February 2026 for large taxpayers, from 1 April 2026 for the others) – the buyer’s NIP is mandatory on all B2B invoices, because KSeF is a system for taxpayers. Invoices for consumers (individuals who do not run a business) you can issue in KSeF or outside it.

Names of goods and services – precision

Article 106e(1) point 8 requires “the name (type) of the goods or service”. In practice this means a description that is understandable and precise, not just the trade name.

• Correct: “IT consulting service – 10 hours – April 2026”
• Not enough: “Service”
• Correct: “Dell Latitude 7440 laptop, 16 GB RAM, 512 GB SSD”
• Not enough: “Computer”

A description that is too general can be a reason for challenging the invoice in a VAT inspection. The tax office must be able to identify what the transaction concerned.

VAT rates 2026

VAT rates in 2026: the standard rate of 23% and reduced rates of 8% and 5%; for selected transactions (for example, an intra-Community supply of goods, exports) – 0%. You can check the rate for a specific good or service in the annexes to the VAT Act or in the binding rate information (WIS).

The rates have been unchanged for many years. The anti-inflation shield that reduced VAT to 0% on food ended in 2024.

Special markings – GTU, MPP, TP

In KSeF (and JPK_V7) some invoices require additional markings:

GTU (Groups of Goods and Services) – sales markings

• GTU_01 – alcoholic drinks (ethyl alcohol, beer, wine, fermented drinks, intermediate products)
• GTU_02 – fuels (Article 103(5aa) of the VAT Act)
• GTU_03 – heating and lubricating oils
• GTU_06 – selected electronic devices and parts and materials for them (listed in Annex 15 to the VAT Act)
• GTU_07 – vehicles and car parts (CN 8701–8708)
• GTU_10 – buildings, structures and land and their parts and shares
• GTU_11 – transfer of greenhouse gas emission allowances
• GTU_12 – intangible services from a closed list (advisory, accounting, legal, management, training, marketing, advertising, market research and others) – excluding IT services
• GTU_13 – transport and warehouse management services (PKWiU ex 49.4, ex 52.1)

You will find the full list of GTU_01–GTU_13 in the regulation on JPK_V7 (§ 10(3)). GTU markings do not appear in the text of the invoice (they are part of the JPK register), but they affect classification in the system.

MPP – the split payment mechanism

Mandatory for invoices covered by Annex 15 above PLN 15,000 gross between VAT payers. Details are in the article Split payment mechanism 2026.

TP – a transaction with a related party

TP is a marking in the JPK_V7 register (transactions between related parties, Article 32 of the VAT Act). It is not an element of the invoice.

The advance invoice and the final invoice

The rule:

• An advance invoice – issued after an advance payment is received, by the 15th day of the following month
• A final invoice – issued after the performance is finally completed

In the final invoice you take into account the advance received (you subtract it from the gross value to be paid). Advance invoices refer to the final invoice by number.

Example:

• FZ/2026/04/0001 – an advance of PLN 20,000 (VAT PLN 3,739.84, net PLN 16,260.16, gross value PLN 20,000)
• FV/2026/06/0001 – a final invoice for PLN 50,000 gross (reduced by the advance of PLN 20,000 – PLN 30,000 to pay)

An invoice in KSeF – the differences

The KSeF number

KSeF assigns every invoice an identifying number (the KSeF number). It does not replace the invoice number given by the issuer – the invoice has both: your company numbering (FV/2026/04/0001) and the KSeF number. The KSeF number is given, among other places, in a corrective invoice, and from 2027 also in transfers for invoices.

PDF visualisation

An invoice in KSeF has no physical paper format – the MF provides a standard visualisation template. The customer downloads the PDF from the KSeF portal.

The duty to receive

The buyer learns of the invoice through the KSeF portal or an email notification. The invoice does not need to be “delivered” as before by letter or email – KSeF acts as the place of delivery. The invoice is deemed issued on the day it is sent to KSeF, and received by the buyer on the day it is given its KSeF number (Article 106na(1) and (3)).

No duty to send it to the customer

Still, in practice many companies send a PDF by email as a duplicate, because:

• The customer may have a delayed synchronisation with KSeF
• An old internal procedure (the accounting department) does not know KSeF
• An invoice for foreign customers – the foreign buyer receives it outside the system, with a QR code

The most common mistakes

1. An error in the NIP – a typo, a missing Polish diacritic – KSeF will reject the invoice
2. Swapping the date of issue and the date of sale – a shift in VAT
3. A name of the goods that is too general – the risk of an inspection
4. No MPP annotation for a value above PLN 15,000 gross from Annex 15 – a penalty of 30% of VAT
5. No GTU markings – errors in JPK_V7
6. The wrong currency for a foreign transaction – wrong conversions
7. An invoice to a non-existent NIP – the buyer is blocked in VAT, MPP is forced
8. A duplicated invoice number – KSeF will reject the second one

KSeF catches some mistakes itself and rejects the invoice with a request for a correction. Errors of substance – a wrongly chosen VAT rate, a wrong GTU classification, a mistake in an amount – require a corrective invoice; they cannot be “undone” after the fact.

Summary

An invoice in 2026 is still an invoice – the mandatory elements of Article 106e have mostly stayed the same (points 26–27 were added from 1 February 2026). The tool changes (KSeF instead of paper/PDF), but the substance is similar. The key to correctness: precise dates, correct NIPs, the right VAT rates, the mandatory markings. You can read about corrective invoices in the article Corrective invoices and correction notes. For a full overview of KSeF obligations see KSeF 2.0 – company obligations. You can stay with your own invoicing program – at Profais we help with the KSeF implementation, and as part of our accounting service we receive invoices from the system.

Sources: ksef.mf.gov.pl, ksef.podatki.gov.pl, podatki.gov.pl, the VAT Act (Articles 106a–106n), MF regulations on the FA(3) structure.