You will get XRechnung & ZUGFeRD e-invoicing integration for your business software
Project details
I build EU e-invoicing systems — and I run one in production.
The images and video above come from my own invoicing SaaS: XRechnung and ZUGFeRD/Factur-X with embedded XML, PEPPOL transmission, KSeF for Poland, DATEV export for German accountants, and an AI assistant that answers VAT questions in the context of the actual invoice. Working software, not portfolio mockups.
I live and work in Germany, so I know the rules your invoice has to survive: mandatory fields under § 14 UStG, reverse charge under § 13b for construction, Kleinunternehmer notes under § 19, Leitweg-ID for the public sector, and the retention questions your Steuerberater will ask.
Typical work: adding e-invoicing to an existing ERP or accounting system, connecting a PEPPOL Access Point, generating hybrid PDFs any recipient can open, and mapping your data to the standard without rewriting your database.
Every document I deliver is validated against EN 16931 before handover — a file that looks right but fails your customer's system is not finished.
I work in English, German and Polish, and I will tell you when something is a bad idea instead of just building it.
The images and video above come from my own invoicing SaaS: XRechnung and ZUGFeRD/Factur-X with embedded XML, PEPPOL transmission, KSeF for Poland, DATEV export for German accountants, and an AI assistant that answers VAT questions in the context of the actual invoice. Working software, not portfolio mockups.
I live and work in Germany, so I know the rules your invoice has to survive: mandatory fields under § 14 UStG, reverse charge under § 13b for construction, Kleinunternehmer notes under § 19, Leitweg-ID for the public sector, and the retention questions your Steuerberater will ask.
Typical work: adding e-invoicing to an existing ERP or accounting system, connecting a PEPPOL Access Point, generating hybrid PDFs any recipient can open, and mapping your data to the standard without rewriting your database.
Every document I deliver is validated against EN 16931 before handover — a file that looks right but fails your customer's system is not finished.
I work in English, German and Polish, and I will tell you when something is a bad idea instead of just building it.
Project Type
OtherWhat's included
| Service Tiers |
Starter
$499
|
Standard
$1,400
|
Advanced
$3,200
|
|---|---|---|---|
| Delivery Time | 7 days | 14 days | 30 days |
Number of Revisions | 1 | 2 | 3 |
Frequently asked questions
About Mariusz
Business Development Manager
Bergheim, Germany - 11:15 pm local time
What sets me apart is that I don’t approach software development purely from a technical perspective. I understand how companies actually operate — how projects are managed, how teams work, where communication breaks down, how much time is lost on administration, and which processes can be improved through automation.
This real-world business experience allows me to design and build software that solves practical problems rather than simply adding more technology.
I specialize in:
Custom ERP & Business Management Systems – solutions tailored to a company's actual workflows and processes
Construction & Project Management Systems – workforce management, tasks, projects, documentation, reporting and operational control
AI Agents & Business Automation – intelligent assistants and automated workflows that reduce repetitive work
AI-Powered Tender & Procurement Solutions – analysis of tenders, requirements, documents and business opportunities
Document & Data Automation – intelligent processing, extraction and analysis of business documents
Invoicing & Financial Workflows – systems that simplify invoicing and administrative processes
CRM & Customer Management – tools for managing leads, customers, communication and sales processes
Mobile Applications – custom Android and iOS applications for businesses, employees and customers
Web & Cloud Applications – scalable platforms accessible from anywhere
AI & LLM Integration – integrating modern AI capabilities directly into existing business processes and software
Custom Business Automation – identifying inefficient processes and replacing repetitive manual work with intelligent digital workflows
My approach starts with understanding the business first.
Before building anything, I look at how the company operates, what employees actually need, where time and money are being lost, and what can realistically be improved.
Because of my background in business development, sales, construction management, project management and team leadership, I can communicate with both management and technical teams and translate real operational requirements into working software.
I don't just build applications.
I build systems designed around how businesses actually work — combining business experience, software engineering and AI to create practical solutions that deliver measurable value.
Steps for completing your project
After purchasing the project, send requirements so Mariusz can start the project.
Delivery time starts when Mariusz receives requirements from you.
Mariusz works on your project following the steps below.
Revisions may occur after the delivery date.
Implementation & validation
I map your invoice data to the chosen standard, implement generation and transmission, then test every document against EN 16931 before delivery. You receive working code, validated sample files and setup documentation.