New feature: spousal splitting as a simulation

Some time ago, we published the article Spousal Splitting in International Comparison to explain where the German splitting model comes from, why it remains controversial, and why tax class choices for married couples often create the wrong incentives. The next step was not another theory piece. It was a tool.

With the new Joint Tax Filing Simulation, you can now see directly how the German splitting model compares with a more individualized tax treatment.

What the new feature does

This page is not just another static explainer and not a classic payroll form. It is a simulation layer for one of the most debated parts of German income tax policy:

• How large is the tax advantage created by the splitting system?
• How does the burden change when incomes are very uneven?
• What happens if the model is reduced, changed or removed?

That is exactly where simulation is more useful than a single example. Instead of one number, you get a clearer view of the pattern behind the policy.

Why this matters

Debates around spousal splitting often jump straight into ideology: does it support families, does it freeze old role models, does it weaken incentives for secondary earners? Those questions matter, but for most households the first question is simpler:

What does this mean for our actual income?

That is the gap this new page closes. It turns an abstract tax-law debate into something easier to read financially.

How this connects to the older blog post

The earlier article focused on three things:

1. the legal and historical background of the splitting system
2. the criticism around labor-market and second-earner incentives
3. the practical differences between tax class 3/5 and 4/4 with factor

The new simulation adds the missing layer. It no longer only asks how the system works. It asks how strong the effect really is under different income distributions.

So the older post still matters. It now works as the conceptual background, while the simulation becomes the practical front end.

Who should use it

This feature is useful well beyond pure tax specialists. It is especially relevant for:

• married couples with a large income gap
• households planning a return to part-time or full-time work
• users following reform debates who want to understand the real financial magnitude
• journalists, advisors and policy-interested readers who need a better intuition for the size of the effect

The more uneven the income split inside the household, the more revealing the simulation becomes.

What to test first

When you open the Joint Tax Filing Simulation, it helps to compare more than one setup:

• a strongly asymmetric income pair
• two similar salaries
• middle-income and higher-income scenarios

That is the fastest way to see where the splitting effect is large, where it almost disappears, and where reform proposals become economically meaningful.

Why we built it

Obolus should not only provide calculators. It should also provide explanation tools that help people reason through policy and household choices. Spousal splitting is exactly the kind of topic where users need more than one static article.

That is why this feature is visual first. It is meant to create orientation before users dive into technical detail.

Conclusion

If you already know the older article, the new Joint Tax Filing Simulation is the natural continuation. If you are new to the topic, you can start with the simulation and then read the spousal splitting background article.

That combination is the real upgrade:

• first see the effect
• then understand the system
• then judge your own household case more clearly