KSeF and selling on Allegro — how to issue invoices

Selling on Allegro with the mandatory KSeF approaching? In this guide we explain when you actually have to issue an invoice and when a receipt is enough, how the National e-Invoicing System changes marketplace invoicing, and what a practical workflow from order to KSeF invoice looks like — with the current timeline for 2026 and 2027.

When does selling on Allegro require you to issue an invoice?

Before we even start talking about KSeF, we need to sort out a basic point that many Allegro sellers get wrong: not every transaction requires an invoice. What you’re obligated to issue depends on who the buyer is and whether they asked for a document.

In online sales, buyers fall into two groups. A consumer (B2C) is a private individual not running a business. A company (B2B) is an entrepreneur who provides their tax ID (NIP) at checkout. This distinction determines everything that happens next.

Consumer (B2C): a receipt is usually enough

A sale to a private individual that you record on a cash register is documented with a receipt. You don’t have to issue an invoice for a consumer automatically — only when the customer requests one. The buyer has up to 3 months to submit such a request, counting from the end of the month in which the goods were delivered or the service was performed. After that deadline, the seller is no longer obligated to issue an invoice.

A request may come through an Allegro message, by email, or in another form. If the customer submits it within the deadline, you cannot refuse. For an invoice issued on request, you normally have until the 15th day of the month following the month of sale, and when the request comes in later — 15 days from the day it was submitted.

Company (B2B): an invoice is mandatory

If the buyer provides a NIP at checkout, you treat the sale as a transaction between businesses and you are obligated to issue a VAT invoice — regardless of whether the customer asked for one. It’s precisely these B2B invoices that will be the first to go into the mandatory KSeF.

The NIP-on-receipt trap

The most common dispute on Allegro concerns a situation where a consumer wants an invoice “for the company” after the fact. Under the regulations (Art. 106b of the VAT Act), you can only issue an invoice with the buyer’s NIP if that NIP was on the receipt at the time of sale. If the buyer didn’t provide a NIP at checkout, you cannot add an invoice with a NIP later — even if they begged you to. You can only issue a personal invoice, made out to a private individual. That’s why your Allegro order form and store terms should clearly communicate that company invoice details must be provided before finalizing the transaction, not after the parcel arrives.

A receipt with a NIP up to PLN 450 is already a simplified invoice

There’s an important exception here that makes life easier with small amounts. A fiscal receipt with the buyer’s NIP whose value does not exceed PLN 450 gross (or EUR 100) is treated as a simplified invoice. For such a transaction, the buying entrepreneur already has a fully valid document for settling VAT, and the seller doesn’t need to issue a separate “regular” invoice for it. It’s worth remembering, because some Allegro buyers ask for an invoice for small purchases even though a receipt with a NIP is entirely sufficient for them.

The KSeF 2026–2027 timeline — from when invoices must go through the system

The National e-Invoicing System (KSeF) is a central government platform through which structured invoices pass (in XML format according to the FA schema). The rollout order was confirmed by the act of August 5, 2025, and it is spread across stages depending on company size.

Receiving invoices: from February 1, 2026

This is a deadline that’s easy to forget, because we focus on issuing. Meanwhile, from February 1, 2026, every entrepreneur must be ready to receive purchase invoices in KSeF. If you buy goods for resale or services on Allegro, your suppliers will start issuing invoices in the system and you must be able to retrieve them from there.

Issuing: February 1 → April 1, 2026 → January 1, 2027

The obligation to issue invoices in KSeF comes in waves:

The key figure is the PLN 10,000 gross per month limit. Until the end of 2026, if the total value of the invoices you issue in a given month does not exceed this amount, you can still issue electronic or paper invoices outside KSeF. Note: this is a “soft” limit. The moment you exceed PLN 10,000 in a given month, every subsequent invoice must already go through KSeF. The smallest entities that permanently stay within this threshold join the obligation only on January 1, 2027.

A practical takeaway for the Allegro seller: if you issue even a few B2B invoices a month for higher amounts, your deadline is most likely April 1, 2026. Don’t plan the rollout “down to the wire” — set aside February and March for testing.

What KSeF really changes for the Allegro seller

Here comes the most important misunderstanding. Many sellers assume that since they issue invoices “in Allegro”, the marketplace will also handle KSeF. That’s not the case.

Allegro does not issue invoices on your behalf

The built-in “Invoices and receipts” module in the Allegro panel generates an ordinary PDF file. It is not integrated with KSeF and such a PDF is not a structured invoice within the meaning of the regulations. Once the obligation takes effect, a document generated solely in this module will not meet the requirement for transactions that must go into the system. It’s you, as the seller, who is responsible for issuing the invoice in the correct format and sending it to KSeF.

In practice this means you need software that pulls order data from Allegro and turns it into a structured invoice sent to KSeF — accounting software with an integration, a dedicated invoicing tool, or a multichannel sales management system. With a dozen or several hundred orders a day, manually retyping data stops being realistic, and every error in a number or amount later means a correction in a government system.

Corrections and returns also go through KSeF

A marketplace is an environment of returns and complaints, so correcting invoices is an everyday occurrence. Two things are worth remembering. First, a correcting invoice to an invoice covered by the obligation must also be issued in KSeF — you won’t correct a document from the system with an ordinary PDF file. Second, in KSeF there are no more “corrective notes” issued by the buyer; minor formal errors (e.g., in address details) are fixed by the seller with a correcting invoice. With a large number of returns on Allegro, this is another argument for the process to be automated rather than pieced together by hand from separate tools.

B2C invoices: voluntary in KSeF, with a QR code for the customer

Good news for stores selling mainly to consumers: invoices for private individuals (B2C) don’t have to go into KSeF. You can issue them outside the system, and voluntarily within it too. There is no penalty for issuing consumer invoices outside KSeF, even after 2026.

If, however, you decide to issue a B2C invoice in KSeF (or your program works that way), the consumer neither has nor needs an account in the system. You then hand them a PDF, a printout, or a link, and on the document you place a QR code or KSeF number, thanks to which they can verify the invoice’s authenticity without logging in. The same applies to any invoice “used outside KSeF” — marking it with a verification code is then mandatory. We covered more on the obligation rules for the whole industry in the article KSeF 2026 for e-commerce sellers.

Practical workflow: from an Allegro order to an invoice in KSeF

Put together into a single sequence, the process looks the same regardless of how many orders you have — only the degree of automation differs. Here’s the sequence worth arranging before April 1, 2026:

1. Pulling the order from Allegro. You gather the transaction data: line items, quantities, amounts, buyer details and — crucially — whether a NIP was provided. This step is best automated through an integration with your Allegro account, so the data flows in on its own.
2. Determining the buyer’s status. NIP present → B2B transaction, invoice mandatory in KSeF. No NIP → consumer; invoice only on request, KSeF voluntary. It’s worth building this condition into the system’s logic, because it’s the most common source of mistakes.
3. Generating the structured invoice. The program creates a document in XML format compliant with the FA schema — not an ordinary PDF. Numbering, VAT rates and data must be correct, because after submission what counts is what the system accepted.
4. Sending to KSeF and assigning a number. The invoice goes to the system, which after verification assigns it a unique KSeF number. Only with this number is the document formally issued.
5. Delivering the invoice to the buyer. A B2B customer retrieves the invoice directly from KSeF. To a consumer you send a PDF or a link with a QR code / KSeF number for verification.
6. Tracking deadlines and bookkeeping. You keep an eye on issuing deadlines (up to the 15th day of the following month, or 15 days from the request) and archive confirmations. KSeF invoices are stored by the system itself for 10 years, but your own records will come in handy anyway.

Offline24 mode — the contingency plan

What if KSeF happens to be down or you lose internet access while packing parcels? An offline24 mode is provided: you issue the invoice outside the system with the date indicated in the P_1 field, and then send it to KSeF no later than the next business day. The system will assign the KSeF number once it receives it. Good invoicing software will handle this automatically — you only see that the document is “waiting to be sent”, and the program retries until it succeeds. Thanks to this, an outage on the system’s side doesn’t block your parcel shipments or force you to halt sales on Allegro.

The most common mistakes with Allegro + KSeF invoicing

• Treating a PDF from the “Invoices and receipts” module as a KSeF-compliant invoice. It’s an ordinary printout, not a structured invoice — for transactions covered by the obligation, it’s not enough.
• Adding a NIP after the sale. If the buyer didn’t provide a NIP on the receipt, you can’t issue them an invoice with a NIP. Make sure the option to provide a NIP is visible already in the cart.
• Overlooking the PLN 10,000 limit. Companies counting on the deferral forget that once the threshold is exceeded in a given month, every subsequent invoice must go through KSeF. Monitor the running total of invoices.
• Ignoring deadlines. The 3 months for the customer to request an invoice and the 15 days for you to issue it are hard deadlines, not suggestions.
• Manual issuing at high volume. With hundreds of orders, retyping data from Allegro into an invoicing tool generates typos in amounts and NIPs that then have to be corrected in a government system.
• No QR code on a B2C invoice delivered outside KSeF. If you share a structured invoice outside the system, marking it with a verification code is mandatory.

Automating this chain — pulling the order, recognizing B2B/B2C, issuing the invoice and sending it to KSeF without manual retyping — is exactly the problem that dedicated tools for KSeF invoicing solve. Nimo (our system for multichannel sellers, in preparation) is being designed precisely around this workflow, but the principle is universal: the fewer manual steps between the order and KSeF, the fewer corrections and the less stress in April 2026.

Frequently asked questions

Does every sale on Allegro require an invoice?

No. For a consumer (a private individual), a receipt is usually enough — you issue an invoice only on their request, which they can submit up to 3 months from the end of the month of sale. For a company that provided a NIP, a VAT invoice is mandatory regardless of whether the customer asked for one.

Do invoices for consumers (B2C) have to go through KSeF?

No. Invoices for private individuals not running a business are excluded from the KSeF obligation — you can issue them outside the system and send them to KSeF voluntarily. If you share such a structured invoice outside the system, place a QR code or KSeF number on it so the customer can verify it.

Does Allegro issue KSeF invoices for me?

No. The “Invoices and receipts” module in Allegro generates only a PDF and is not integrated with KSeF. Issuing the structured invoice and sending it to the system is your responsibility — you need accounting software or an invoicing tool with Allegro and KSeF integration for it.

From when do I have to issue invoices in KSeF if I have small sales?

Most companies — from April 1, 2026. If the total value of your invoices doesn’t exceed PLN 10,000 gross per month, you can issue them outside KSeF until December 31, 2026, and the smallest entities within this threshold join the obligation from January 1, 2027. The largest taxpayers (over PLN 200 million in sales) start as early as February 1, 2026.

What should I do when KSeF is down or I have no internet?

Use offline24 mode: you issue the invoice with the date indicated in the P_1 field and send it to KSeF no later than the next business day. The system will assign the KSeF number once it receives the document. It’s worth having your invoicing software do this for you automatically.