Backend Intern: Improve the AI Engine That Catches Pay Errors

Salary Unpaid

Help improve the AI that finds the errors humans miss.

Pay errors are common, yet very few payslips ever get checked. At PayTjek we use AI and machine learning to find those errors in seconds, so trade unions can catch them and set things right for their members. As our backend intern, you will help make that engine even better.

About PayTjek

PayTjek checks payslips and employment contracts against Danish collective agreements. We combine the latest within AI and machine learning with a deterministic rule engine: AI reads documents and extracts the rules from collective agreements, and the rule engine makes sure the result is correct. Not a model that guesses. Our customers are trade unions that use PayTjek to find pay errors for their members and document them so a claim can be raised. The system checks 12 payslips in 90 seconds.

Korrekthed. Ikke sandsynlighed. Correctness, not probability.

We are a young company with big ambitions. Our goal is to make payslip checks a natural part of what every trade union offers its members, first in Denmark and then across Europe. You will work alongside a small team of highly skilled people, with a background in formal verification from DTU, and you will have real influence from day one. Our first full-time developer started with us as an intern.

What you will work on

AI and machine learning for document understanding: OCR, rule extraction and turning legal text into rules
Connecting the rule engine to our case flow
APIs and data models for payslips, contracts and collective agreements
Testing and quality assurance of rules

Who you are

You know Python
Experience with cloud, Docker and containers is a plus
You are curious about AI, machine learning and correctness
Most important of all: you are eager to learn and not afraid to dive into something new
You are able to work from our office in central Copenhagen

What we offer

Hands-on work with the newest technology within AI and machine learning
Real tasks in a product used by real customers
Daily sparring with skilled colleagues, including our CTO and backend developer
A real opportunity of employment after the internship, just like our first full-time developer
A front row seat in a startup on its way up

This is an unpaid internship.

How to apply: Apply here on The Hub with a short motivation and your CV or GitHub.

Questions? Feel free to call me, Theis Veddinge, Co-founder and CEO, on +45 61 54 19 23.

For more information or questions please contact us at theis@paytjek.io or phone number +45 61 54 19 23

Perks and benefits

This job comes with several perks and benefits

Near public transit

Remote work allowed

Central office

Free coffee / tea

Skill development

Flexible working hours

Working at
PayTjek

See company profile

PayTjek verifies payslips and employment contracts against Danish collective agreements, with a level of certainty that probabilistic AI cannot offer. Korrekthed. Ikke sandsynlighed. Correctness, not probability. The problem Pay errors are widespread, yet very few payslips ever get checked. Collective agreements are complex, and checking payslips by hand is slow work for trained case handlers. As a result, trade unions only reach a small fraction of the payslips where errors hide, and members lose money they are owed. Our solution PayTjek is an internal tool for trade unions. We combine the latest within AI and machine learning with a deterministic rule engine: AI reads documents and extracts the rules from collective agreements, and the rule engine validates every rule and every calculation. Members upload their payslip through an app. The case handler works in a case flow where every error comes with a direct reference to the relevant clause in the collective agreement and a plain explanation, so the case handler can act right away and has the documentation ready to raise the claim. Member and union can follow up with each other directly in the flow. This lets trade unions offer payslip checks as a natural part of their membership offering, at a scale that was not possible before, without adding pressure on their resources. Our ambition We are a young company with big ambitions. We start with Danish trade unions and the Danish labour market, and our goal is to make payslip verification a standard part of what unions offer their members across Europe. PayTjek was founded in Copenhagen in 2025 by Theis Thøger Veddinge and Anton Gammelmark Andersson, with roots in research on formal verification, and is supported by Innovationsfonden.