VAT Engine journal

EU VAT, explained for builders

Technical and operational guidance for teams building VAT-aware products.

VAT Engine blog cover comparing today's VAT rate with the rate selected for an original transaction date.

Article · 11 min

Current VAT Rate vs Transaction-Date VAT Rate: Why the Difference Matters

Today's VAT rate is not necessarily the rate you should use for an older transaction. Learn why transaction dates, historical evidence, and provenance matter.

By Vasyl Kyryliuk · Published Oct 24, 2026

VAT Engine blog cover illustrating the fields that make a VAT calculation record explainable, including amounts, rate, date, source, and provenance.

Article · 11 min

What Should a VAT Calculation Record Actually Contain?

A VAT result is more useful when you can explain it later. Here is what a calculation record should preserve beyond the final tax amount.

By Vasyl Kyryliuk · Published Oct 8, 2026

VAT Engine cover comparing floating-point money arithmetic with integer minor-unit calculations for predictable VAT results.

Article · 13 min

Why Money Calculations Should Not Use Floating Point

Binary floating point is useful for many problems, but risky as a canonical money representation. Learn why minor units and explicit rounding make VAT calculations more predictable.

By Vasyl Kyryliuk · Published Oct 2, 2026

VAT Engine cover comparing VAT-exclusive pricing, where VAT is added to net, with VAT-inclusive pricing, where VAT is extracted from gross.

Article · 11 min

VAT-Inclusive vs VAT-Exclusive Pricing: The Math Developers Get Wrong

VAT-inclusive and VAT-exclusive prices require different formulas. Learn how to calculate net, VAT, and gross correctly without common rounding and percentage mistakes.

By Vasyl Kyryliuk · Published Sep 25, 2026

VAT Engine Journal cover illustrating how country, product, and transaction date feed into a VAT API to produce rate, context, and evidence.

Article · 7 min

Why a VAT API Needs More Than a Rate Lookup

A practical look at why production VAT APIs need more than a country-to-rate lookup: tax classes, transaction dates, pricing context, evidence, and reviewable decisions.

By Vasyl Kyryliuk · Published Sep 12, 2026