The true cost of building your own e-invoicing solution – and why it adds up fast

For many European software vendors, e-invoicing starts as a straightforward product decision. There's a mandate coming up, or clear customer demand otherwise.

A few formats. A few connections. A first new market to support. How hard can it be?

Launching e-invoicing might not be challenge, but everything that comes after usually proves to be one.

What often begins as a contained development project quickly turns into up-keeping long-term infrastructure with regulatory, operational, and commercial implications that are easy to underestimate. We break down where the real cost of building your own e-invoicing solution in Europe comes from, and why it tends to grow over time.

Launch is just beginning, and the easy part

Most teams plan for the first release: schemas, validations, connections, testing. That work is visible, scoped, and fits neatly into a roadmap.

E-invoicing in Europe evolves constantly and that means that e-invoicing is not a "build once and move on" feature. There's ViDA, national mandates, Peppol, and as many local interpretations of it as you can count. And they all move on different timelines. 

In practice what that means is ongoing work. Once you go live, you take ownership of something must continuously adapt to new rules, markets, and growing volumes (if you are lucky). Your team's to-do list quickly expands to include things like:

• Tracking regulatory timelines and scope changes
• Updating document formats and validation rules
• Handling country-specific exceptions
• Re-certifying connections and networks

Even within the EU, requirements rarely change in sync and that is something you need to prepare for already before you launch.

Supporting a format is not the same as running e-invoicing

Invoicing is a business-critical part of your customers' day-to-day business. There's very little room for error. If something breaks, your customers notice and you are expected to fix it.

Once you operate e-invoicing in production, you deal with identifier lookups, routing logic, acknowledgements, retries, and failures across different networks. Each additional customer and country increases the number of things that can go wrong.

Not to mention the operational work that comes with it: monitoring, incident response, support, and audit readiness. None of this is particularly visible during initial planning, but once your customers start using it at scale, you can't escape it. For many vendors e-invoicing can start to feel like a separate system that they are running alongside their actual product. 

Scaling is the tipping point

Most development teams can cope with this workload for a while, but usually the tipping point comes with growth. This can be through increased invoice volumes from customers, more users on your platform, or expanding across country borders. 

Let's take internationalisation as an example. It can be manageable to build a solution for your local market, but often the second or third country exposes the complexity of e-invoicing. There's different rules, different formats, different expectations, and what might have worked well before will need some serious rethinking.

That's typically when software vendors reassess their original approach.

Build your own, use a gateway, or embedded API?

Broadly speaking, there are three common ways for software vendors to handle e-invoicing:

1. Build and operate everything themselves
2. Use a basic gateway for delivery only
3. Embed a partner API that manages compliance, routing and operations

There are obviously technical differences, but the main question is how much long-term responsibility do you want to carry: is e-invoicing something you want to maintain actively, or simply enable to your customers?

The key takeaway

Building e-invoicing in Europe is rarely expensive on day one. It becomes expensive through accumulation: regulatory change, operational overhead, and cross-border expansion. Not because teams misjudge the first release, but because the lifecycle is longer and heavier than it looks.

Understanding that early makes it easier to choose an approach that still works when your product, customers, and markets grow.