KSeF and PIP, how the tax inspectorate will automatically spot your B2B contracts

In short and to the point:
  • KSeF (Krajowy System e-Faktur, the National e-Invoice System) becomes mandatory for issuing invoices from 1 February 2026 for companies with 2024 turnover above PLN 200 million, from 1 April 2026 for other VAT payers, and only from 1 January 2027 for the smallest JDGs (Jednoosobowa działalność gospodarcza, sole proprietorships) with turnover up to PLN 10,000 a month. Receiving invoices through KSeF is already mandatory for everyone from 1 February 2026¹.
  • KSeF itself doesn’t analyze risk or “signal” anyone: it only stores structured invoice data. The analysis and transfer of that data to PIP (Państwowa Inspekcja Pracy, the National Labour Inspectorate) are handled by two separate, specific laws: the new Article 68ac of the Social Insurance System Act (ZUS, Zakład Ubezpieczeń Społecznych, Poland’s Social Insurance Institution) and the new Article 299j of the Tax Code, both of which entered into force on 8 July 2026².
  • The algorithm only performs a sorting function, deciding who to check first: it doesn’t make the reclassification decision. The final determination always requires a separate evidentiary proceeding by a PIP inspector, including checking the actual working conditions under Article 22 § 1 of the Labor Code³.
  • Three invoice patterns raise inspection priority the most: all turnover going to a single buyer’s tax ID, an identical amount and issue date month after month, and an unchanging service description text in the invoice’s mandatory field⁴.
  • The PKWiU field (service classification code) in the KSeF invoice structure is itself optional, so it isn’t the main source of risk. The main signal comes from the combination of amount, date, and buyer, not from the presence or absence of a code⁵.
  • Legal protection already exists now, not only after an inspection: Article 14b of the PIP Act lets you request an individual interpretation from the Chief Labour Inspector for PLN 40, with a response within 30 days, before an algorithm raises your case up the priority list⁶.

Why KSeF kicks in earlier than PIP’s new powers

The time gap between mandatory KSeF and PIP’s new powers means that, by the time of the first possible inspection under the new law, data on your invoices has already been accumulating for months. The obligation to issue invoices through KSeF for the vast majority of VAT payers, including nearly all JDGs, took effect on 1 April 2026¹. PIP’s new powers to administratively establish an employment relationship took effect on 8 July 2026, more than three months later.

The practical consequence is simple and rarely accounted for in advance: by the time an inspector first gets the right to check a specific contractor after 8 July 2026, KSeF already holds at least three to four months of that contractor’s invoice history to the same buyer. For large companies with turnover above PLN 200 million, this period is even longer, since KSeF has applied to them since 1 February 2026. This isn’t a hypothetical risk for “someday in the future,” it’s a database already built up as of the day you’re reading this article.

KSeF doesn’t wait for the new PIP law: by the day an inspector gains the power to reclassify a contract, the history of your invoices has already been sitting in the system for months.

What PIP and KAS technically see in your KSeF invoice

KSeF stores every invoice as a structured file, not as an image or PDF, and that’s exactly what makes mass comparison of invoices technically trivial. Every structured e-invoice (faktura ustrukturyzowana) follows a single logical schema, FA(3), which contains a mandatory field, P_7, “the name or type of the goods or service,” up to 512 characters per invoice line⁴. This field can’t be left blank: without it, an invoice technically won’t pass through KSeF. Every invoice also always includes the buyer’s tax identification number (NIP), the issue date, the amount, and the currency.

That means that for any tax number in the system, it’s possible to automatically compile: how many different buyers were invoiced during the year, what the amount of each invoice was, what text recurs in field P_7, and how often. None of this requires an inspector to manually open a file: all the data is already in text, structured form in the KAS (Krajowa Administracja Skarbowa, the National Tax Administration) database, which technically administers KSeF.

There’s also a separate PKWiU field (Polska Klasyfikacja Wyrobów i Usług, the Polish Classification of Products and Services), used to describe the subject of the invoice more precisely. This field is optional under the FA(3) structure: the VAT Act doesn’t require it to be filled in, and most JDGs don’t fill it in at all⁵. A practical conclusion that’s often missed follows from this: leaving the PKWiU field blank isn’t protection, because the analysis relies primarily on the mandatory P_7 field, the amount, and the date, not on the optional classification code.

Three invoice patterns that automatically raise inspection priority

Risk isn’t raised by invoices in KSeF as such, but by a specific combination of three features, visible only because the data is structured and automatically comparable.

Pattern 1, all turnover to a single tax ID

When a JDG’s income structure, month after month, consists 100% of invoices to the same buyer, the analytical system classifies such a contract as a potential substitute for an employment contract⁴. This is the strongest of the three patterns, because it’s visible at a glance from a list of issued invoices, with no need to open any contract.

This lines up with feature 1 from the checklist “7 signs your B2B contract is disguised employment,” where we write about a practical benchmark of 80% or more of income from one client as the first risk feature. The difference is that KSeF shows the exact percentage by tax ID automatically, rather than the contractor’s own subjective estimate of their income. When KSeF shows exactly 100% to a single tax ID over a year or more, that’s no longer an approximate estimate, it’s an exact figure the system sees first.

Pattern 2, identical amount and date, month after month

Cyclically issuing an invoice on the same day of the month for exactly the same amount over an extended period is, to the analytical system, a sign of fixed salary rather than payment for a variable scope or outcome of work. In real business turnover, the amount and date of an invoice naturally vary depending on the number of hours worked, completed stages, or options chosen by the client.

This is the direct technical counterpart to feature 7 from the same seven-features checklist, “a fixed invoice amount regardless of outcome.” The seven-features article explains this feature from the perspective of the contract and working practice. Here we explain the same fact from a different angle: why this feature in particular is technically the easiest to detect automatically through KSeF, since comparing the date and amount in two text fields requires no understanding of the content of the work, just matching numbers.

Issuing an e-invoice through the KSeF system on a laptopIssuing an e-invoice through the KSeF system on a laptop

Pattern 3, an unchanging service description text

When field P_7 contains exactly the same text, for example “Software development services under the contract,” in every single invoice without exception over a year or more, it looks like a job-description text rather than a description of a variable scope of completed tasks. A real business invoice for project work usually describes a specific stage, module, or result, rather than repeating one generic line every month.

Example. A company receives invoices from contractor Karol every month: an amount of PLN 16,500, an issue date always on the 28th, and a service description always “Usługi programistyczne zgodnie z umową” (software development services under the contract). This is what the invoices look like for 16 months in a row, and there’s no other buyer in Karol’s invoices. Does this create high priority for the analytical system?

Yes. All three patterns are present at once: one buyer at 100%, an identical amount and date, an identical description text. This is exactly the combination the PIP-ZUS-KAS analytical system is trained to raise to the top of the inspection priority list.

The opposite example: contractor Bazyli invoices four different companies over the course of a year, each invoice’s amount varies from PLN 7,000 to 21,000 depending on the project stage completed, and the service description describes a specific module or outcome: “Building the authorization module, stage 2 of 3” in one month, “Fixing critical post-release defects” in another. Does this create high priority?

No. None of the three patterns is present: multiple buyers, a variable amount, a variable description. This doesn’t guarantee the absence of other legal risks, such as a fixed schedule or direction, which KSeF doesn’t see at all, but from the invoice structure alone, the analytical system gets no priority signal here.

Does KSeF itself send a “signal” to PIP, or is a person needed

No, there’s no technical mechanism that automatically sends a PIP inspector a notification every time an invoice matches one of the three patterns. KSeF and its associated analytics perform only a sorting function, deciding who to check first, and the final decision is always made by a person.

The legal structure here has two layers, and the confusion arises precisely because both layers sound similar. The first layer is the Chief Labour Inspector’s (GIP, Główny Inspektor Pracy) obligation to draw up annual and multi-year PIP action programs aimed at targeted, risk-based inspections⁷. Data from KSeF, through the ZUS-PIP-KAS data-exchange system (Article 68ac) and through KAS’s telecommunication transmission to ZUS and PIP (Article 299j of the Tax Code), feeds precisely this layer: it influences which businesses and contractors end up on the priority list for inspection planning².

The second layer is conducting the inspection itself and issuing the decision. Here, no KSeF data by itself decides anything: a decision on the existence of an employment relationship is issued by the inspector only after an evidentiary proceeding that assesses the actual working conditions against the four features of Article 22 § 1 of the Labor Code, not the invoice structure³. Even if the inspection is conducted remotely, using the new law’s option to require an online transmission of documents and interviews with the parties, this is still the act of a specific inspector, not an automatic algorithmic conclusion⁸.

Example. Imagine an analytical system raised a company up the priority list because of 22 contractors with an identical amount and a single buyer each. Does this mean PIP will automatically issue a decision reclassifying all 22 contracts without an inspection?

No. The priority list only determines the order in which to inspect. The inspector still assesses each contract separately based on actual working conditions, and it’s possible that some contractors genuinely show the features of an independent business, despite an identical invoice structure, for example due to a genuine absence of a fixed schedule or direction.

We’ve already written, in the series article “Who risks losing B2B status after the PIP 2026 reform,” about the new Article 68ac of the Social Insurance System Act, which links ZUS, PIP, and KAS into a single risk-analysis system². Here it’s worth adding a detail that article doesn’t cover: Article 68ac itself governs data exchange within ZUS, while the specific channel through which tax data from KSeF invoices reaches this system is a separate new Article 299j of the Tax Code (Ordynacja podatkowa), which directly obliges the head of KAS to transmit data from the Central Tax Data Register to ZUS and PIP via telecommunication².

These two laws work as a pair: Article 299j opens the technical data-transfer channel, while Article 68ac defines exactly what ZUS and PIP use this data for, risk analysis for labor-law violations, employment legality, tax law, and social insurance. Both entered into force at the same time, on 8 July 2026, together with the main part of the new PIP law.

What to do if your invoicing already looks “typical”

  1. Check your own invoice history in KSeF over the last 12-16 months. Calculate the share of turnover to a single tax ID and how often the amount, date, and service description text recur. The KSeF Taxpayer Application is available for reviewing your own issued invoices without an additional intermediary.
  2. Change your payment structure from a fixed monthly amount to payment by stage or outcome. A different amount each month removes the strongest of the three patterns without changing the substance of your cooperation with the client.
  3. Detail the service description field (P_7) to match the work actually performed each month, rather than repeating one generic line. This isn’t cosmetics for an algorithm, it’s a more precise, more business-like description of what you actually did.
  4. Don’t rely on a blank PKWiU field as protection. This field is optional and has little effect on inspection priority by itself: the main signal comes from the amount, date, and buyer, not the presence of a classification code.
  5. If you’re confident in your working model, consider requesting an individual interpretation from the Chief Labour Inspector under Article 14b of the PIP Act before an algorithm raises your case up the priority list: a description of the actual work situation, a PLN 40 fee, a response within 30 days⁶.
  6. If you’re a company owner or HR and you see this exact invoicing pattern in several contractors at once, that’s a systemic risk, not an isolated case: more on the scale of this risk in the series article “Who risks losing B2B status after the PIP 2026 reform,” and on specific fix steps, in the series article “How to fix a B2B contract under PIP 2026.”

Frequently asked questions

Does a specific PIP inspector see my invoice in KSeF directly, as soon as I issue it?

No. An inspector doesn’t review invoices one by one in real time. The data flows into the general ZUS-PIP-KAS analytical system, which builds priority lists for inspection planning. A specific inspector sees specific invoices only within the scope of an already-opened inspection of a specific business.

Can I avoid the risk by simply not filling in the PKWiU field?

No, that doesn’t work, because the PKWiU field is already optional and isn’t the main source of the signal. The risk is created by the combination of the amount, the invoice issue date, and concentration on a single buyer in the invoice’s mandatory fields, not by the presence or absence of an additional classification code.

Does this only apply to IT contractors?

No, the mechanics are the same for any industry where a JDG issues invoices through KSeF. We cover specifics for IT contractors in particular, including payment through foreign payment platforms like Deel, in the series article “PIP 2026 and the IT industry: why developers are in the highest-risk zone.”

Does an identical invoice amount automatically mean a fine or reclassification?

No. It raises inspection priority, but the reclassification decision itself always rests on the actual working conditions under Article 22 § 1 of the Labor Code: schedule, direction, place of work, personal performance. An invoice by itself isn’t evidence of an employment relationship, only a signal of who to check first.

I genuinely only have one client for objective reasons, for example an exclusive one-year contract. Does that alone settle the matter?

No. A single client raises inspection priority but isn’t an independent basis for a decision. If you also don’t have a fixed schedule, direction from a manager, and a personal obligation to perform, the chances of defending your business status remain, though it’s worth going through an inspection carefully and preparing documents in advance.

How much does a mistake cost if an inspection is scheduled and an employment relationship is found?

Besides ZUS and tax back-payments calculated under separate limitation-period mechanisms, the fine for disguising an employment relationship as a civil-law contract ranges from PLN 2,000 to 60,000, and if the affected worker is registered as a debtor in maintenance arrears in the National Debtors Register, up to PLN 90,000⁹. A detailed breakdown of the fine scale is the subject of a separate series article on the size of PIP fines in 2026.

What to do with this information

Checking your own invoice history in KSeF takes less than one business day, but gives an exact answer to whether your working model technically looks like a typical signal for the analytical system. MojaFirma offers two formats depending on your situation.

If you work on a JDG yourself. The basic format is an online B2B audit: fill out a questionnaire about the structure of your clients and invoices, and within 48 hours get a report with a risk category and three priority recommendations.

If you’re the owner or HR of a company with several B2B contractors. Assessing systemic risk requires a larger format, a B2B operating model audit, which checks contracts, invoices, and contractors’ KSeF history all at once, rather than one contract in isolation.

Fill out the B2B audit questionnaire

Sources

  1. Act of 11 March 2025 amending the Act on Tax on Goods and Services and certain other acts, Dz.U. 2025 poz. 1203 (mandatory KSeF deadlines); Ministry of Finance, National Tax Administration, announcement “Mandatory KSeF postponed to 1 February 2026”; National e-Invoice System, scope of mandatory KSeF
  2. Social Insurance System Act, Dz.U. 2026 poz. 199, Art. 68ac (added by Art. 5(6) of the Act of 11 March 2026, Dz.U. 2026 poz. 473, effective 8 July 2026); Tax Code (Ordynacja podatkowa) of 29 August 1997, Dz.U. 2025 poz. 111, Art. 299j (added by Art. 4 of the Act of 11 March 2026, Dz.U. 2026 poz. 473, effective 8 July 2026)
  3. Labor Code, Art. 22 § 1; Act of 11 March 2026 amending the Act on the National Labour Inspectorate and certain other acts, Dz.U. 2026 poz. 473, Art. 1(2) (new Art. 33a of the PIP Act, the inspector’s evidentiary proceeding); Forsal.pl, “Algorithms serving PIP: how data from ZUS and KSeF will automatically flag companies for employment-form inspections,” 2026 (practical source material, not a legal act)
  4. National e-Invoice System, information brochure on the FA(3) logical structure, field P_7 (Fa/FaWiersz); Deloitte, expert practical training “How to cooperate under B2B in light of the PIP reform and the introduction of KSeF,” 12.05.2026 (practical source material, not a legal act)
  5. National e-Invoice System, structured invoice and FA logical structure, the PKWiU field as an optional element
  6. Dz.U. 2026 poz. 473, Art. 1(2) (new Art. 14b of the PIP Act, individual interpretations from the Chief Labour Inspector)
  7. Dz.U. 2026 poz. 473, Art. 1(2) (amended Art. 18(1)(3) of the PIP Act, annual and multi-year inspection programs based on risk analysis)
  8. Dz.U. 2026 poz. 473, Art. 1(2) (new Art. 23(1)(2a) and new Art. 26(5-8) of the PIP Act, remote inspections)
  9. Dz.U. 2026 poz. 473, Art. 3 (amending Art. 281 § 1 and § 2 of the Labor Code, fines of PLN 2,000-60,000 and PLN 3,000-90,000)

Legal status as of: August 28, 2026.

This article does not constitute legal advice. Every situation is individual and depends on the specific contract and circumstances. Author: Valerii Kushnirskyi, in-house legal practitioner at MojaFirma.