What KSeF doesn't carry: the cost documents an accounting office still has to chase

KSeF Closed One Door

The pitch for KSeF in accounting offices was simple: the invoices come to you. No more chasing clients for a folder of paper on the 8th of the month. For domestic VAT invoices between companies, that's mostly true now. The download runs, the XML lands in the books, and nobody has to ask.

The trouble is that "mostly" hides a whole category of documents. KSeF carries structured invoices issued by Polish VAT taxpayers who are obliged to use it. Everything else still arrives the old way: by email, as a photo, in a glovebox, or not at all. And because the KSeF part now runs itself, the rest is what gets forgotten.

This week I've been writing about the gaps inside KSeF itself: offline24 invoices that fall between two download runs, and correction invoices you now have to wait for. This post is about the gap around it.

Five Kinds of Document That Bypass KSeF

In 2026 a client's purchase documents fall into two groups: the ones KSeF delivers and the ones it never will. The second group has five parts.

1. Foreign suppliers. A seller with no seat and no fixed establishment in Poland isn't obliged to use KSeF. That covers most of what a modern small company pays for by card: ad platforms, cloud hosting, design tools, software subscriptions, marketplace fees, and the EU supplier of goods. These invoices sit in a supplier portal or an email notification, often behind a login only the client's owner has. They're also the ones where timing matters most. For an import of services the VAT point follows the service, not the date the PDF shows up, and for monthly subscriptions that means the end of each billing period. An invoice found in March for a January service still belongs to January.

2. Cash-register invoices and receipts with a NIP. Until 31 December 2026 an invoice can still be issued from a cash register outside KSeF, and a receipt carrying the buyer's NIP up to 450 zł gross still counts as a simplified invoice. That's fuel, parking, the hardware store, lunch with a client. Small amounts, a lot of pieces, and they live in the client's wallet.

3. The smallest sellers. Until the end of 2026 a seller whose monthly sales on invoices stay under 10,000 zł gross may keep invoicing outside KSeF, on paper or as a PDF. The local mechanic, a freelance translator, the one-person IT support firm. Here's the catch: one month over the limit and that seller is in KSeF for the rest of the year. So the same supplier can send September's invoice by email and October's through KSeF, and nobody tells the buyer.

4. Permanent exclusions. Single-journey passenger tickets and motorway toll receipts that act as invoices are outside KSeF by design, and they stay outside after 2027 too. So does an invoice issued to the owner as a private person without the company's NIP. Issuing B2C invoices in KSeF is voluntary, and even when the seller does it, the invoice doesn't reach the company's KSeF because the NIP is the delivery address.

5. Documents that were never invoices. Payroll, ZUS, bank fees, bills for civil-law contracts, business-trip settlements, customs documents on imports. KSeF didn't change any of them, but they used to arrive in the same monthly folder as the invoices. Now the folder's gone, and some clients have stopped sending anything at all because they assume KSeF handles it.

That last habit is what worries me most. I've heard some version of it in several offices this year: the client stopped sending documents in April because "you have KSeF now".

Count and Value Tell Different Stories

Here's an example, not a statistic. A twelve-person software company has 70 cost documents in a month. 41 arrive through KSeF: rent, leasing, the accountant's own invoice, hardware, a telecom bill. The other 29 don't: ads, three cloud subscriptions, two SaaS tools, eleven fuel and parking receipts, train tickets, a PDF from a freelance designer, and the payroll set.

By count, 41% of that client's documents are outside KSeF. By value it might be 15%. The office thinks in value. The work is in the count. Each missing piece is a separate request, and each one blocks a JPK line or a cost deduction.

Measure it across your own portfolio before you decide it doesn't matter. The numbers will swing wildly from client to client. A distribution company that buys everything from domestic wholesalers may be at 5%. A marketing agency that lives on foreign software may be at 60%. As with the month-end close, the spread between two clients in one office tells you more than any average.

The Duplicate Nobody Notices

There's a second problem, and it comes from the fact that the email inbox has to stay open.

Many Polish suppliers still email a PDF next to the invoice they issued in KSeF. Since the KSeF mandate the structured invoice is the invoice, and the PDF is just a picture of it. But the office still has to work through that inbox for the five categories above. So the PDF gets booked on Tuesday, and on Wednesday the KSeF download books the XML.

Nothing fails. There's no error message. The client has a cost twice and VAT deducted twice, and it surfaces at the year-end reconciliation, or at the tax office.

The fix is cheap and has to happen before booking, not after: deduplicate on seller NIP plus invoice number plus gross amount across both sources. If a document from the inbox has a Polish NIP and a KSeF number exists for that key, the PDF is an attachment, not a document. I'd put that rule in place before anything else in this post.

What 1 January 2027 Changes

On 1 January 2027 three of the five categories shrink sharply:

• invoices can no longer be issued from cash registers,
• a receipt with a NIP up to 450 zł stops being a simplified invoice (the seller has to issue a proper KSeF invoice, and the receipt is just a receipt),
• the 10,000 zł monthly exemption ends.

What stays outside: foreign sellers, tickets and toll receipts, B2C invoices without a NIP, and everything that isn't an invoice. So the list you build for collecting documents needs an expiry date. Whatever you set up now for fuel receipts will be the wrong process in three months. The foreign-supplier part won't be.

Start From the Bank, Not the Inbox

The most reliable way I know to find missing documents is to stop looking for documents and look at money leaving the account instead. Almost every cost leaves a trace on a bank statement or a card statement before anybody thinks to send the invoice.

This is the read-only check I set up for offices, running on the third business day of the month:

1. Take every outflow from the previous month: transfers and card transactions from the client's statements. If you already import MT940 files, the data is there; bank statement automation covers the import side.
2. Match each outflow against the purchase invoices already in the books from KSeF: by the payee's NIP or account number, then by amount and date window.
3. Sort what doesn't match into four groups: foreign supplier (non-Polish IBAN or a merchant abroad), small domestic seller, fuel/parking/travel receipt, and payments that need no invoice (ZUS, tax office, salaries, internal transfers). The last group is removed from the list; it's where most false alarms come from.
4. Hand the bookkeeper one list per client: client X, 7 card payments with no document, 4 of them foreign subscriptions, total 2,140 zł. The bookkeeper sends it on. After a couple of months, when the false-hit rate is low, the list can go to the client automatically as a neutral statement of what's missing.

The agent books nothing and decides nothing. It turns "the client forgot" into a list with amounts and dates, before the 10th instead of after the 20th. You need nothing more than the connector that already pulls invoices (automatic KSeF downloads) and one bank feed.

Two Numbers for This Week

1. For your three biggest clients: what share of last month's cost documents arrived outside KSeF, by count and by value? If you can't answer without opening folders, that's the answer.
2. How many outgoing payments from September have no document in the books today? Count them on the 3rd business day of October, and again on the 10th. The gap between those two counts is how much chasing your office does.

Want the bank-side check running for your clients? Write to me. It's the obvious next step once the KSeF download is in place.