## How to Submit a Quarterly Update to HMRC's Making Tax Digital API Four times a year, every sole trader and landlord in Making Tax Digital (MTD) for Income Tax has to send HMRC a summary of their income and expenses. The first deadline of the 2026-27 tax year, 7 August, has already passed, and the second lands on 7 November. Each of those summaries is a single API call from software to HMRC, and getting that call right is what this tutorial is about. You can follow it without any earlier reading. The one-time setup every MTD integration needs (a sandbox application, an OAuth 2.0 access…