Final Week Q1: Last Chance to Fix Records Before 7 August

You Have About Five Weeks Left - Here Is What to Do With Them

The 7 August 2026 deadline for your first MTD quarterly update is close enough to feel real now. If your records are mostly in order, this post will help you do a final sweep and submit with confidence. If your records are still a bit rough around the edges, this is exactly where to focus your energy. We will cover the last reconciliation steps, what happens after you submit, how the amendment window works, and what you genuinely cannot change once the deadline has passed.

Start With a Simple Reconciliation Check

Before you submit anything, go back through your records for the full Q1 period - 6 April 2026 to 5 July 2026 - and ask yourself three questions.

1. Does every bank receipt that relates to your trade or property income appear in your records?
2. Does every expense you are claiming have a corresponding receipt, invoice, or bank entry?
3. Do your totals match what your bank statements actually show?

This sounds basic, but a surprising number of first-time filers discover small gaps at this stage - a few invoices not recorded, a cash payment missed, or a bank transfer that got miscategorised. Fixing these now, before submission, is far easier than dealing with them afterwards.

If you have mixed income from both self-employment and property, the reconciliation process has a few extra steps. Our post on final-week Q1 reconciliation for mixed income covers those in more detail.

Common Things People Miss at This Stage

• Small cash income that was never logged - particularly common for tradespeople and market sellers
• Expenses paid from a personal account rather than a business account
• Mileage for business trips that was never written down at the time
• Bank charges, subscriptions, or software costs that count as allowable expenses but were overlooked
• Rental income received in June but not added to the records until July

For a fuller list of what you can and cannot claim, the post on allowable expenses for MTD is worth a quick read before you finalise your figures.

The Pre-Submission Checklist

Once you have reconciled your records, run through these checks before you hit submit.

• All income figures are gross, not net of any fees or platform deductions
• Any deposits you hold as a landlord are not included as income (deposits are not yours until deductions are agreed)
• Expenses are categorised correctly - repairs versus improvements, for example
• If you are using simplified mileage rates, your mileage log covers all journeys claimed
• You have not accidentally included any personal expenditure in your business costs

We have a dedicated pre-submission checklist post at Q1 final checks before 7 August if you want to go through each item in more detail.

What Happens After You Submit on 7 August

Once you have submitted your Q1 quarterly update, HMRC acknowledges receipt. No tax is due immediately as a result of the quarterly update itself - the update feeds into a running picture of your income, but it does not trigger a payment. Tax payments on account work on their own schedule, which is explained in our post on MTD quarterly updates versus payments on account.

After submission, you enter what is sometimes called the amendment window. This runs from the day you submit through to 31 August 2026. During this period, you can go back into your MTD software and correct errors in what you submitted.

The Amendment Window: 7 to 31 August 2026

If you realise after submitting that you made a mistake - a missing invoice, a wrongly categorised expense, an income figure that was slightly off - you can amend your Q1 quarterly update during August. HMRC allows this. You are not stuck with whatever you submitted on 7 August.

The process for doing this through AffordableMTD is straightforward. You correct the figures in your records and resubmit the update. HMRC receives the revised version and that replaces the earlier one. There is no penalty for making an amendment during this window.

For a step-by-step walkthrough of how to do this, see our post on amending your Q1 MTD update before 7 August - many of the same principles apply for post-submission amendments through August.

What You Cannot Amend After Filing

The amendment window gives you time to correct honest mistakes, but it does not cover everything. There are a few things that fall outside what can be changed through an amendment.

• The period itself. You cannot change the fact that a quarterly update covers 6 April to 5 July. If you accidentally included income or expenses from outside that period, you correct the figures - but the dates of the period are fixed.
• Allowances and reliefs that require a formal claim. Some adjustments - such as capital allowances on certain asset purchases - cannot simply be added through an amendment. These go through the annual declaration at the end of the tax year.
• Anything submitted after 31 August. Once the amendment window closes, Q1 is locked for quarterly update purposes. Any corrections after that point form part of your final declaration process on 31 January 2027.

If you are unsure about what allowances and adjustments are available to you for Q1, the post on Q1 allowances and adjustments for August 2026 has a clear breakdown.

The Difference Between a Quarterly Update and Your Final Tax Return

This is something a lot of first-time MTD filers get anxious about, and it is worth being clear on. Your quarterly update is not the same as your tax return. It is a summary of your income and expenses for that period. It feeds into HMRC's records, but it does not finalise your tax position.

Your actual tax liability is calculated once a year, through the final declaration. That is where you add in other income, claim personal allowances, and settle any tax due. The quarterly updates are checkpoints, not final verdicts.

This means if your Q1 figures are slightly off, it is not a disaster. You have the amendment window, and beyond that, the final declaration. The system is designed with the expectation that not everything will be exact at the quarterly stage.

For a fuller explanation of how these two things relate to each other, see quarterly updates versus final declaration explained.

Record Retention: What You Must Keep for Q2 and Beyond

Once Q1 is filed, your attention shifts to Q2, which covers 6 July to 5 October 2026. But Q1 does not disappear once submitted. HMRC can ask questions about any period within the current tax year, and potentially going back further if they open an enquiry.

The records you need to keep include:

• All invoices and receipts for income received during Q1
• All receipts, invoices, and bank statements supporting your expense claims
• Your mileage log, if you claimed mileage
• Any tenancy agreements, rent statements, or deposit records if you are a landlord
• Bank statements covering the full Q1 period
• A copy of what you submitted - your software should hold this, but keep a local copy too

HMRC expects you to keep these records for at least five years after the 31 January filing deadline for the relevant tax year. For the 2026-27 tax year, that means keeping Q1 records until at least January 2033.

Our post on HMRC record-keeping standards for MTD goes into the specific requirements in more detail, including what formats HMRC accepts.

Digital Records and What "Keeping" Means in Practice

MTD requires you to keep digital records. That means your income and expense data needs to exist in a digital format - not just a paper shoebox. It does not mean every single receipt has to be scanned, but your financial records themselves must be digital.

If you are using AffordableMTD, your records are stored within the software. You should also back up any source documents - photos of receipts, PDF invoices, bank statement exports - somewhere safe and accessible. Cloud storage works well for this.

For more on what happens if HMRC asks questions after you file, see preparing records for HMRC enquiries after Q1 filing.

Getting Q2 Started on the Right Foot

You do not need to wait until Q1 is filed before starting Q2. In fact, the best approach is to treat Q2 as already underway - because it is. Q2 runs from 6 July to 5 October 2026, and if you are reading this in early July, that period has already started.

The habits you build for Q1 carry straight into Q2. Keep logging income as it comes in. Photograph receipts on the day you get them. Reconcile your bank statement weekly rather than leaving it to the last month.

If you want to set up a solid routine from the start of Q2, the post on Q2 MTD week one: get your records right from today has a practical framework.

If You Are Still Worried About Getting Q1 Wrong

A lot of first-time filers feel a level of anxiety about their first quarterly update that is out of proportion to the actual consequences. Here is a realistic picture of what "getting it wrong" actually means.

If you submit and then spot a mistake, you have until 31 August to fix it. If you miss something and only discover it later, it goes into the final declaration. If HMRC has a question about something, they will contact you and you will have the chance to explain. The system is not set up to punish honest people who make genuine errors in their first year.

What HMRC does take seriously is non-filing, deliberate under-reporting, and failing to keep any records at all. Submitting something in good faith and correcting it later is not in that category.

If you missed the deadline entirely or are worried about late filing, the post on what happens if you miss the 7 August deadline covers that scenario directly.

For a look at the most common errors people make at this stage and how to avoid them, Q1 MTD submission errors and common mistakes is worth a read before you submit.

Pulling It Together Before 7 August

You have the time to do this properly. The final week before 7 August is the right moment to stop adding to your records and start checking them. Reconcile your income against your bank statements. Check your expenses are categorised correctly. Make sure you have not missed anything obvious. Then submit.

After that, use August to correct anything that needs correcting. Keep your Q1 records somewhere safe and accessible. And get Q2 underway with the same habits that will make the next deadline easier than this one.

The first quarterly update is the hardest one - not because it is complicated, but because it is unfamiliar. By the time Q2 comes around, you will know exactly what you are doing.