Fixing errors in Making Tax Digital for Income Tax in QuickBooks

Transitioning to quarterly reporting with Making Tax Digital for Income Tax (MTD for IT) is a big change. It is normal to have questions about accuracy or what to do if you realise you've missed something.

The good news is that MTD for IT is designed to be flexible. This guide covers how to resolve common issues and how to use QuickBooks to help keep your records accurate for HMRC.

I missed an expense from a previous quarter

If you find a receipt or invoice that should have been included in a quarter you’ve already submitted, don't worry. You do not need to "re-open" or resubmit that specific quarter.

• The solution: Simply add the transaction to QuickBooks with its correct date.
• How it works: Because MTD updates in QuickBooks are submitted as cumulative (year-to-date) figures, the missing amount will be automatically picked up and included in your next quarterly update provided you’re still in the same tax-year.

I see something is missing (e.g. CIS deductions)

If you are a subcontractor under the Construction Industry Scheme (CIS), you might notice your deductions aren't showing in your quarterly summaries.

• The reason: Quarterly updates focus on your gross income and allowable expenses.
• The solution: CIS deductions "suffered" are not part of the quarterly summary. You will review and claim these credits during the Final Declaration stage at the end of the year to reduce your final tax bill.

How do I manage the 1-5 April gap? (31 March Year-End)

If your accounting year ends on 31 March, your first Making Tax Digital year (2026/27) may  have a tiny 5-day "gap" between 1 April and 5 April 2026 if your reporting follows the tax year.

• The first year rule: Your MTD obligations officially start on 6 April 2026. Any transactions from 1–5 April 2026 should be reported as a separate "Business Source Adjustable Summary" (BSAS) in QuickBooks.

I categorised a transaction incorrectly

If you submitted an update and later realised a "Travel" expense should have been "Office Supplies," you can fix it easily.

1. Locate the transaction in your Expenses or Banking tab.
2. Change the category to the correct one.
3. QuickBooks will note this change. When you prepare your next quarterly update, the "Year to Date" totals will reflect the corrected categories, ensuring HMRC has the right data by the end of the year.

Dealing with submission errors

If you see an error message when trying to submit, check these three things:

• "403 Forbidden": Your "digital handshake" with HMRC has expired. Go to Income Tax settings and select Re-authorise.
• "Pending" status: HMRC's servers can be slow at peak times. Wait 72 hours for a "Success" receipt before attempting to resubmit.
• "Individual is not Mandated": This usually means you haven't yet completed the "Sign up" process on the HMRC website, even if you have a Government Gateway ID.

I missed a submission deadline

HMRC is introducing a points-based penalty system to make the transition fairer.

• Points, not immediate fines: If you miss a deadline, you will typically receive one penalty point. You only receive a financial penalty (usually £200) once you hit a certain threshold of points.
• The 2026 "soft landing": To give you time to learn the system, HMRC will not apply late submission penalty points for the first four quarterly updates (April 2026 – April 2027).

Pro tips

• Nil updates: If you had no business activity for three months, you must still submit a "Nil" update to tell HMRC you are still compliant.
• Mapping questions: Use the Preview tax mapping feature in the Income Tax centre to see exactly which HMRC "box" your QuickBooks categories are assigned to.
• Digital links: Never fix an error by "copy-pasting" or manually typing into an HMRC portal. Always make the change inside QuickBooks so your digital link remains unbroken.

More help

• Resource Hub: Visit our Making Tax Digital for Income Tax Resource Hub for step-by-step setup guides, FAQs, and the latest HMRC timeline updates.
• QuickBooks Community: Making Tax Digital (MTD) Drop-In Q&A Session
• Expert Support: If you need to speak to a person, find out more about how and when to contact QuickBooks Online support.
• Digital Assistant: Need quick answers while you work? Chat with our Digital Assistant 24/7 by selecting Help (?) within your QuickBooks account.