When you open your quarterly update, Sage shows a date range for the period so far.
The range always starts on the first day of the tax year, not the first day of your quarter. This is because each update is cumulative.
Your start date depends on your reporting periods:
The range ends on the day before the current date (yesterday), not the last day of your quarter. This end date moves forward each day until you submit.
Making Tax Digital (MTD) for Income Tax requires cumulative updates. Each update is a running total from the start of the tax year, not a snapshot of one quarter.
So each update includes:
Each new update replaces your previous total for the tax year. So you can correct or add transactions in a later update. You don't need to change an earlier one.
Your update includes all year-to-date figures up to yesterday. This fulfills your quarter one obligation and provides an accurate tax estimate based on your latest records. Updates are cumulative, so any future submissions to HMRC updates all records from the beginning of the tax year.
The main point is that you submit an update before each quarterly deadline. You can resubmit as many times as you need before your end-of-year tax return.