If you've built against HMRC's Making Tax Digital APIs, you've seen the phrase "Fraud Prevention Headers" in the docs and probably assumed it was a checkbox exercise — a handful of headers, a quick lookup table, done. It isn't. Get these wrong and HMRC either silently downgrades your submission...
Source: [Dev.to](https://dev.to/virendravyas/what-hmrcs-fraud-prevention-headers-actually-require-that-the-docs-dont-tell-you-1kn9)