Mass checks of sick notes in 2026 - a new reality
2026 has brought a revolution in the way the Social Insurance Institution (ZUS) verifies whether sick notes are justified. The figures for the first quarter are alarming - the number of withdrawn sickness benefits rose by 40 per cent compared with the same period of the previous year. This is no coincidence, but the result of introducing advanced technological tools that have radically changed how effective the checks are.
The previous model relied mainly on inspectors visiting sick people at home and on randomly selecting cases for verification. Today the heart of the whole system is artificial intelligence, which analyses hundreds of variables in a fraction of a second and flags the sick notes that raise the greatest doubts. For thousands of Poles this means decisions requiring them to repay benefits received, together with interest.
If you are on sick leave or are planning to use it, you need to know the new rules of the game. One ill-considered step - a photo on social media, an invoice issued during your illness or not being at the right address - can cost you the loss of your benefit for the entire period of sick leave. Below we explain how the new system works and what to do so as not to fall into the trap.
ZUS's digital detective - how does the AI algorithm pick out suspicious L4 notes?
In 2026 ZUS definitively abandoned the random selection of people for checks in favour of a precise system based on artificial intelligence algorithms. The new mechanism analyses huge data sets and looks for anomalies that may indicate abuse of the right to sickness benefit. The patterns most often detected include sick notes issued just before long weekends, e-sick notes from doctors in distant regions of Poland and repeated series of short L4 notes from different specialists.
A particularly significant change is the integration of the AI system with the National e-Invoicing System (KSeF). This means that if you run a business and issue even a single invoice while on sick leave, the algorithm will detect it immediately. For ZUS, issuing an invoice is hard evidence of performing gainful work during a period of incapacity for work, which automatically results in the loss of the benefit for the entire period of sick leave.
What is more, the algorithm also takes into account your history of previous sick notes, your age, your occupation and even your social media activity. The system runs continuously and processes data from many sources simultaneously in real time. This means that the chances of going unnoticed are minimal today.
Social media photos as evidence against you
One of the most common and at the same time most costly mistakes made by people on sick leave is posting photos on social media. Many insured persons wrongly assume that the annotation "patient may walk" (the so-called code 2 on the sick note) entitles them to any physical and social activity. Nothing could be further from the truth.
What does code "2" on a sick note really mean?
In line with settled case law, sick leave serves solely for recuperation, that is, returning to health. Code "2" only means that the patient does not have to stay in bed and may carry out basic daily activities - a visit to the pharmacy, grocery shopping or a follow-up appointment with a doctor. Recreation, travel, family events or sporting activity are not permitted, even if you subjectively feel better.
Online monitoring by special ZUS units
In 2026 ZUS has special units monitoring online activity. They use facial recognition and geolocation analysis tools. Screenshots of your Instagram stories, Facebook posts or photos shared in public groups become full evidence in administrative proceedings. Importantly, even archive photos may be wrongly interpreted by the algorithms as documentation of current activity. That is why your social media profile should be set to private, and during sick leave it is best to refrain completely from posting anything at all.
An inspection at your door - traditional visits by ZUS inspectors
Despite advancing digitalisation, physical checks at the place of residence have not become a thing of the past. On the contrary - in 2026 ZUS inspectors are visiting sick people more and more often, including in the evening and on Saturdays. Surprise is part of a strategy designed to maximise the effectiveness of verification.
The biggest trap remains the wrong address of stay during illness. If you went to stay with your parents or partner during recuperation, and the doctor entered your registered address on the sick note, your absence during an inspection will automatically be treated as abuse. In such a situation you have only 3 days to submit written explanations. A receipt from a pharmacy or grocery shop showing the time of purchase can confirm a short absence related to meeting basic daily needs.
Remember, however, that going to the hairdresser, the cinema, the gym or a restaurant does not fall into the category of essential activities and means an immediate suspension of benefit payments. That is why it is crucial to manage your behaviour consciously throughout your sick leave.
How to appeal against a ZUS decision? Step-by-step procedure
Receiving a negative ZUS decision does not mean the case is lost. Polish law guarantees the right to appeal, but it requires decisive and well-considered action. Here are the key steps:
- Appeal deadline - you have 30 days from the date the decision is delivered to file an appeal with the labour and social insurance court through the ZUS branch that issued the decision.
- Medical records - gather full documentation confirming that your conduct during illness was justified. If, for example, you walked in a forest and your doctor recommended physical activity as part of treatment for depression, a written medical recommendation is key evidence.
- Burden of proof - remember that in appeal proceedings it is up to you to prove that your activity was consistent with the purpose of the sick leave.
- Legal assistance - fighting a precise AI system and ZUS's extensive control apparatus requires professional support. Consulting a lawyer specialising in social insurance law significantly increases the chances of a favourable outcome.
It is worth knowing that the labour courts are not uncritically favourable to ZUS. With solid medical arguments and properly prepared documentation, winning the case is entirely possible.
A practical guide - how to avoid losing your benefit in 2026
To avoid problems with ZUS while on sick leave, follow these rules:
- Check the address on the sick note - make sure the doctor has entered the address where you will actually be staying during your illness. If you change your place of stay, inform ZUS immediately.
- Understand what the codes mean - code "2" (patient may walk) allows only activities essential to daily life: a visit to the doctor, the pharmacy, basic shopping. Recreation and travel are not allowed.
- Stay silent online - do not post any photos or stories on social media, even archive ones. Set your profiles to private.
- Do not issue invoices - if you run a business, any gainful activity during L4 means automatic loss of the benefit.
- Keep receipts - document every trip out of the house with a receipt showing the time, which will confirm the purpose and duration of your absence.
Following these rules minimises the risk, but does not eliminate it completely. The ZUS control system in 2026 is tighter than ever, so prevention and legal awareness are your best defence.
Need legal help? Contact us
If you have received a ZUS decision withdrawing your sickness benefit or requiring you to repay benefits received, do not delay taking action. The deadline for appeal is only 30 days, and every day of delay reduces your chances of an effective defence.
Our firm specialises in social insurance law and has many years of experience in handling cases against ZUS before the labour courts. We help with preparing appeals, gathering medical records and representation in court. Contact us today - a free initial consultation will let you assess your chances and plan your strategy.
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