RPV Calculator

When a Belgian court case ends, the losing party pays the winner a lump sum toward their lawyer's fees: the rechtsplegingsvergoeding, or RPV. The amount looks simple but isn't. It depends on the bracket of the amount in dispute and on which of four rate scales applies (one general scale and three for social security cases before the labour courts), and the judge chooses between a minimum, a base and a maximum. On top of that, the amounts follow the consumer price index: each time the index rises ten points, every amount goes up from the first day of the next month. Lawyers and bailiffs were looking up PDF tables, checking which indexation applied on the date of the judgment and doing the arithmetic by hand. Mistakes are easy to make, and AI assistants make them too: they quote outdated amounts or miss an indexation.

I built one small, pure calculation core and put everything else around it. The core knows the Belgian royal decree that sets the amounts (the Koninklijk Besluit of 26 October 2007), the 2024 amendment that changed how indexation works, and every indexation since 2007, and it reads the live consumer price index from Statbel, Belgium's statistics office. A server route fetches the Statbel data, because direct calls failed in Safari on iOS, and a tolerant parser finds the right columns whatever labels Statbel uses. When Statbel switched the series to another base year, which made every month look like a new indexation, the parser learned to rebase it to 2004 = 100. Tests check the amounts to the cent against the official table of the College van de hoven en rechtbanken, the body that manages Belgium's courts. The website and the AI connector call the same core, so they always give the same answer.

• Calculator: the minimum, base and maximum for all four rate scales, special cases such as a claim that cannot be valued in money, a judgment given because the other party did not appear (verstek), or a claim the other party accepted before the case was entered in the court's register (inschrijving op de rol), and the amounts in force on any past date, for example on appeal.
• Every calculation lives in the URL, so it can be shared as a link, and a local history keeps earlier ones. Results can be copied, printed or shared.
• Rate table: every bracket of the four rate scales, rendered on the server so search engines see the amounts, with copy, print and CSV download.
• Indexation: a chart of the consumer price index, the progress toward the next threshold and a forecast of when the next indexation takes effect, with the method explained.
• FAQ: who pays, appeals, judgments given when a party did not appear, criminal cases, VAT and the history of the law, answering the questions practitioners actually ask.
• AI connector: a remote MCP server, listed in the official MCP Registry, with three tools. In Claude, ChatGPT and Mistral Vibe the answers appear as compact cards in four languages, with a chart for the indexation.
• Quality: available in Dutch, French, German and English, tested with axe against WCAG 2.2 AA on every page and component in light and dark mode, with unit, component and end-to-end tests on every change.

The RPV Calculator has been live since the summer of 2024 and grew, over more than 300 commits, from a single calculator into a complete reference for the procedural indemnity: free and without an account. Since October 2026 it also works inside AI assistants, which now call the real calculation instead of guessing the tariffs.