Standard and calendar MTD updates use different coverage dates but the same deadlines. Select calendar periods in the software before sending the first update if that is the correct basis. Once an update is sent, HMRC does not allow a change for the rest of that tax year.
The two reporting options
Standard periods follow the tax year. For 2026/27, the cumulative second update covers 6 April to 5 October 2026 and is due by 7 November 2026. Calendar periods suit an accounting period from 1 April to 31 March. The corresponding second update covers 1 April to 30 September 2026 and has the same deadline.
The later updates also build on the year so far. A third standard update covers 6 April 2026 to 5 January 2027; it is not just the transactions since October. The calendar equivalent runs from 1 April to 31 December 2026.
Can you switch after filing?
HMRC says to select calendar periods in compatible software before sending the first quarterly update. Once an update has been sent, you cannot change the periods for the rest of that tax year. If a previous accountant has already filed, check the existing setting before creating replacement records.
What to give your accountant
Provide your accounting year-end, the reporting basis already selected and copies of any earlier submission confirmations. A bank statement ending at month-end does not, by itself, establish which HMRC reporting periods you use.
For example, a landlord keeping monthly records may prefer calendar periods. That preference still needs to be reflected correctly in the software; it should not be assumed from how the landlord names folders.
Keep the dashboard and submission dates consistent
Your service dashboard may display separate work stages for each quarter. Those stages should not be confused with the cumulative totals sent to HMRC. Ask your accountant to confirm both the period being reviewed and the year-to-date coverage of the submission.
Before changing providers, tell TaxSimba whether any update has already been submitted. This helps the accountant continue the existing reporting basis without accidentally omitting or duplicating days.
Check the basis already used in software
Illustrative preparation example.
Before comparing an export with an update, recover the first submission and the selected standard or calendar basis. A period ending on 30 September is not interchangeable with one ending on 5 October. Keep the same basis visible throughout the year.
Check: Which reporting basis does the existing submission evidence show?
| Check | Practical action |
|---|---|
| Which period option is actually selected? | Check the software and earlier submissions rather than inferring it from file names. |
| Do records cover the cumulative window? | Reconcile from the relevant start of year through the update end date. |
| Has the first update already been sent? | Confirm the existing setting before making a provider or software change. |
Are calendar periods just different submission deadlines?
No. They change the date coverage. The published submission deadlines are the same for the corresponding update.
Can a new accountant choose a different basis mid-year?
Not simply after an update has been sent. Supply the current setting and submission history so the year continues consistently.
Download a checklist for this guide
- Record the accounting year-end and chosen periods.
- Save the current software setting.
- List earlier update acknowledgements.
- Check each cumulative start and end date.
- Share the period choice during any handover.