After Your Q1 MTD Filing: Prepare Records for HMRC Enquiries

You've Filed Q1 - Now What?

Most sole traders and landlords breathe a sigh of relief after hitting send on their Q1 quarterly update. The deadline is gone, the figures are in, and the next one feels far away. But HMRC does not simply receive your update and move on. They can - and do - open enquiries into income, expenses, and allowances. Not always immediately, and not always predictably. The good news is that being prepared takes far less effort than most people expect, as long as you do not wait until the letter arrives.

This post explains what records to keep after Q1, how to organise them so you can actually find things, and what tends to trigger HMRC attention in the first place.

Why HMRC Might Ask Questions After a Quarterly Update

A quarterly update under Making Tax Digital for Income Tax is not a full tax return. It reports your income and expenses for the period - but it does not settle your tax liability. That happens at the final declaration stage. However, HMRC has access to your quarterly figures as soon as you submit them, and patterns that look unusual can flag for review.

Enquiries can be opened at any point - not just after the final declaration. HMRC may cross-reference your figures against bank data, third-party income reports from platforms like eBay or Airbnb, or simply compare your numbers with similar businesses in your sector.

If you want a clear picture of how quarterly updates fit into the wider filing picture, the post on MTD quarterly updates vs full tax return is worth reading first.

Common Enquiry Triggers

• Expenses that are high relative to your income, particularly for home office or vehicle costs
• Income that is lower than previous years without an obvious explanation
• Rental income that does not match figures from letting platforms
• Mileage claims that seem high for your type of work
• Mixed income (self-employment and property) where figures between the two do not add up clearly
• Large or irregular expense categories with no supporting detail

None of these automatically mean an enquiry. But they are the areas where HMRC tends to focus when something does not look right.

What Records to Keep - and for How Long

HMRC does not expect perfection. They expect evidence. The question they are asking when they open an enquiry is simple: can you show us that the figure you claimed was real and allowable?

For Sole Traders

• Invoices and receipts for every expense you have claimed. Digital copies are fine - a photo of a paper receipt saved to cloud storage counts.
• Bank statements showing the payments went out. These corroborate your receipts.
• Mileage logs if you are claiming vehicle costs using simplified rates. Date, destination, purpose, and miles covered.
• Invoices issued to clients - or records of income received if you do not use formal invoicing.
• Contracts or engagement letters where relevant, particularly for larger or ongoing work.
• Records of any adjustments you made to your quarterly update, including why you made them.

If you use simplified mileage rates rather than actual vehicle costs, the rules are explained in the post on mileage allowances and simplified rates in Q1.

For Landlords

• Tenancy agreements for each property, including start and end dates.
• Rent receipts or bank records showing rent received each month.
• Receipts and invoices for repairs, maintenance, letting agent fees, and any other allowable costs.
• Mortgage statements if you are claiming finance costs.
• Evidence of void periods where income dropped - emails, letting agent correspondence, adverts placed.
• Records of capital improvements even if not deductible as revenue expenses - these matter at disposal.

There is a full breakdown of what HMRC expects from landlords facing enquiries in the post on HMRC rental income enquiries and the records you need.

How Long to Keep Everything

The standard HMRC guidance is five years after the 31 January filing deadline for the relevant tax year. In practice, keeping records for six years is safer. If HMRC suspects deliberate under-reporting, they can go back 20 years. That is not something most people need to worry about - but it is a reason not to delete things casually.

How to Organise Your Records So You Can Actually Find Them

Keeping records is one thing. Being able to produce them quickly under pressure is another. An HMRC enquiry typically gives you 30 days to respond with the information requested. If your receipts are scattered across email folders, a box under the desk, and three different apps, that is a stressful 30 days.

A Simple Folder Structure

Whether you use cloud storage, a shared drive, or just folders on your computer, a consistent structure helps. Something like this works for most sole traders and landlords:

• One top-level folder per tax year (e.g. "2026-27")
• Sub-folders for each quarter (Q1, Q2, Q3, Q4)
• Within each quarter: income, expenses (by category if helpful), bank statements, mileage
• A separate folder for annual items: tenancy agreements, insurance documents, mortgage statements

This is not complicated. The point is that if you receive an enquiry letter about a specific quarter, you can go straight to the right folder rather than searching across your entire digital life.

Naming Files Consistently

File names like "receipt.jpg" or "invoice.pdf" become useless quickly. Something like "2026-07-14_BQ_Tools_£45.jpg" takes five seconds longer to type and saves hours later. Date first (so files sort chronologically), then supplier, then amount.

Matching Records to Your Quarterly Update

Once you have filed your Q1 update, keep a copy of what you submitted alongside the records that support it. If you later amend it - which is entirely possible and covered in the post on amending your Q1 update before 7 August - keep a record of both the original and the amended version, with a note explaining the change.

Expenses That Attract Scrutiny - and How to Defend Them

Some expense types are more likely to prompt questions than others. It is worth knowing which ones these are, and making sure your records are particularly solid in these areas.

Home Office Costs

If you work from home and claim a proportion of household costs, you need to be able to explain how you calculated that proportion. HMRC's simplified flat rate is easier to defend than an apportionment of actual bills - but whichever method you use, document it. Write down your reasoning at the time, not retrospectively.

Vehicle and Mileage Costs

Mileage claims without a mileage log are difficult to support. HMRC expects a contemporaneous record - something kept as you go, not reconstructed from memory later. Your log should show the date, where you went, the business purpose, and the miles driven. A simple spreadsheet or app works fine.

Repairs vs Capital Improvements (Landlords)

This is one of the most common areas of dispute for landlords. Replacing a broken boiler with a like-for-like model is a repair. Upgrading to a more efficient system with extra features may be a capital improvement. The line is not always obvious, but the principle is: if you are restoring something to its original condition, it is likely a repair. If you are improving on what was there before, it may not be deductible as a revenue expense.

Allowable vs Non-Allowable Expenses

Not everything you spend money on for your business or property is allowable against tax. Personal costs that overlap with business use need to be apportioned. The post on allowable expenses for MTD covers the detail of what you can and cannot claim.

Mixed Income Situations

If you have both self-employment income and rental income, HMRC looks at both together. Inconsistencies between the two - or figures that seem to have been shifted between them without good reason - can attract attention. Keep your records separate and clearly labelled by income source.

If this applies to you, the post on mixed income and MTD for landlords with self-employment covers the setup considerations in more detail.

If HMRC Does Open an Enquiry

An enquiry letter does not mean you have done anything wrong. HMRC runs enquiries on a random basis as well as targeted ones. The letter will specify what they want to look at and give you a deadline to respond.

The key things to do when you receive one:

1. Read it carefully and note the response deadline.
2. Identify which tax year and which income/expense areas they are asking about.
3. Gather the relevant records - invoices, bank statements, mileage logs, tenancy agreements.
4. Respond to exactly what was asked. Do not volunteer extra information beyond the scope of the enquiry.
5. If the figures are correct, say so clearly and provide the supporting evidence.
6. If you find an error while preparing your response, it is better to acknowledge it and correct it than to hope HMRC does not spot it.

If you are unsure how to respond, or if the enquiry covers a complex area, consider speaking to a tax adviser before replying. A professional can help you respond accurately without inadvertently expanding the scope of the enquiry.

Staying Organised Between Now and Q2

The best time to prepare for a potential HMRC enquiry is not when the letter arrives - it is right now, while the Q1 period is still fresh. Set aside an hour to check that your records for April to June are complete, filed sensibly, and backed up somewhere secure.

If you found your Q1 records were messier than they should have been, the post on fixing messy expense records before August is a practical starting point. And if you are already looking ahead, Q2 planning and preparing records for the July deadline covers what changes from 6 July onwards.

The habit of keeping clean, organised records throughout each quarter - rather than scrambling at deadline time - makes both your quarterly updates and any potential enquiry response significantly easier to handle.

The Short Version

Filing your Q1 quarterly update is not the end of the process - it is a snapshot that HMRC can revisit. The way to handle that confidently is not to file differently, but to keep clear records that back up what you submitted. Invoices, receipts, mileage logs, bank statements, tenancy agreements - kept in a sensible folder structure, backed up, and held for at least six years. If you do that consistently from the start of each quarter, an HMRC enquiry becomes a paperwork exercise rather than a crisis.