Why Proof Matters More Than the Claim Itself

Claiming an expense in your MTD quarterly update is straightforward. Proving it to HMRC if they ask is a different matter entirely. Many DIY filers assume that if they've submitted their figures, the job is done. But HMRC can open a compliance check months or even years after you file - and when they do, they will ask for evidence. Not the figures. The evidence behind them.

This guide covers exactly what proof HMRC expects for common expense types, how to store it between quarterly updates, and what to do if you've already claimed something but can't put your hands on the receipt. If you've ever looked at a shoebox of paper and wondered which bits actually matter, this is for you.

What HMRC Actually Means by "Evidence"

HMRC does not specify a single approved format for expense records. What they require is that you can show, clearly and convincingly, that an expense was genuinely incurred for business purposes. That usually means you need something that confirms three things:

In practice, this evidence comes in several forms. Receipts and invoices are the most obvious, but they are not the only acceptable proof.

Receipts

A receipt is what you get after paying - typically a till receipt from a shop or a printed confirmation from an online order. It shows the date, the amount, and the items or services purchased. Receipts are the most common form of expense evidence for smaller purchases: stationery, tools, subscriptions, travel snacks on a work trip, and so on.

HMRC accepts digital photos of paper receipts. You do not need to keep the physical paper. A clear photograph taken on your phone is sufficient, as long as the key details are legible.

Invoices

An invoice is what a supplier sends you before or when requesting payment - it is a formal request for money. Invoices typically include more detail than receipts: the supplier's name and address, your name, an itemised breakdown of the services or goods, the date, and a unique invoice number.

For larger expenses - a contractor doing work on your property, a web designer you've hired, an accountant (if you use one) - you will usually have an invoice rather than a receipt. Keep these carefully. They are strong evidence because they are specific to you.

Bank and Credit Card Statements

Bank statements show payments leaving your account. On their own, they are not always enough - a statement entry showing "£45.00 - Amazon" does not tell HMRC what you actually bought. But combined with a receipt or invoice, they confirm that the payment actually happened.

Statements are also useful as backup when a receipt has been lost. If you can show the payment on your statement alongside other context (a screenshot of the order confirmation, an email from the supplier), that combination may be sufficient.

Mileage Logs

If you claim business mileage using HMRC's simplified mileage rates (currently 45p per mile for the first 10,000 miles in a car), you cannot use fuel receipts as evidence. Instead, you need a mileage log - a record of each business journey that shows the date, start and end points, reason for the trip, and number of miles.

A simple spreadsheet works. So does a note in your phone or a paper logbook. The point is that you can reconstruct each individual journey if asked. Vague totals ("I drove about 3,000 miles for work") will not hold up. For more on how mileage claims work in MTD, see our guide to mileage allowances for MTD.

Photographs

For some expenses - particularly repairs or maintenance for landlords - a photograph can be genuinely useful supporting evidence. A photo of a broken boiler before it was replaced, or damaged flooring before it was repaired, helps establish that the work was genuinely needed.

Photos work best alongside an invoice from the contractor who did the work. On their own, they are supplementary rather than primary evidence. But do not underestimate how useful they can be in a compliance check, particularly when the nature of a repair is disputed. Landlords should also read our guide on repairs vs capital works in MTD for context on why the distinction matters.

Contracts and Agreements

If you pay a regular business expense under a contract - a lease on a business premises, a service agreement with a software provider, a rental agreement for equipment - keep the signed contract or written terms. These help confirm that the expense is ongoing and legitimate, not a one-off personal purchase dressed up as a business cost.

Which Expenses Need the Strongest Proof

Not every expense carries equal scrutiny risk. HMRC is more likely to question expenses that are large, unusual, or involve a personal element. Here is a rough guide to where the bar is higher:

Note: Using HMRC's flat rates for some expenses (like simplified mileage or the home working allowance) removes the need for itemised receipts for those specific costs. If you are unsure which flat rates apply to your situation, see our post on allowable expenses for MTD.

How to Store Expense Evidence Between Quarterly Updates

MTD requires you to file a quarterly update roughly every three months. Your evidence needs to last much longer than that - HMRC requires self-employed people and landlords to keep records for at least five years after the 31 January submission deadline for the relevant tax year. That means records from the 2026-27 tax year need to be kept until at least 31 January 2033.

Keeping records organised between quarterly updates is where many DIY filers slip up. Here is a simple system that works without specialist software:

Go Digital From the Start

Paper receipts fade, get lost, and take up space. The easiest way to protect your records is to photograph every receipt or invoice as soon as you receive it. A clear smartphone photo saved to a dedicated folder is all you need.

Name your files clearly. Something like 2026-07-15_boiler-repair_£480_PlumbersLtd.jpg is immediately identifiable and searchable. Vague filenames like "receipt1.jpg" will cause you problems eighteen months later.

Use a Folder Structure That Mirrors the Tax Year

Create a folder for the tax year (e.g. "MTD 2026-27"), then subfolders for each quarter (Q1 April-June, Q2 July-September, etc.), then within each quarter, subfolders by expense category. When you file each quarterly update, you then know exactly which folder holds the supporting evidence for that period.

For more on building a record-keeping structure that holds up over time, see our guide to setting up a record-keeping system for MTD.

Back Up to the Cloud

A single copy stored only on your phone or laptop is a risk. Devices fail. Use free cloud storage (Google Drive, iCloud, Dropbox - or whichever you already use) to keep a second copy. This also protects you if your original paper receipt is ever needed but has since faded or been lost.

Reconcile Monthly, Not Quarterly

Trying to gather three months of evidence in the week before your quarterly update deadline is stressful and error-prone. A better habit is to spend twenty minutes at the end of each month matching your expenses to your bank statement and confirming the evidence file is complete. Problems are much easier to fix when they are a few weeks old rather than months old. Our post on bank reconciliation for MTD walks through the matching process step by step.

Warning: Cloud storage is not the same as backing up. If you only save files in one place - even in the cloud - and that account is compromised or accidentally deleted, you lose everything. Keep at least two copies in two different locations (e.g. your laptop and cloud storage, or two different cloud services).

What to Do If You've Lost Proof for an Expense

It happens. You claimed an expense in good faith, but now the receipt is gone - you can't find it on your phone, the email confirmation has been deleted, and the supplier isn't responding. What do you do?

First, don't panic and don't remove the expense from your records. Removing it creates a different problem (an understated expense) and may not even be possible after a deadline has passed. Instead, work through these steps:

Step 1: Try to Reconstruct the Evidence

In many cases, you can find enough to reconstruct a clear paper trail even if the original receipt is gone.

Step 2: Write a Contemporaneous Note

If you genuinely cannot recover formal evidence, write a clear note explaining what the expense was, why it was for business, how much it was, and why you no longer have the original proof. Date the note and keep it with your records. HMRC may still question the expense, but a written explanation is better than nothing and shows you are acting in good faith.

Step 3: Decide Whether to Retain or Remove the Claim

If you have some corroboration (a bank statement entry plus a supplier name and a plausible business reason) and the amount is modest, most DIY filers will reasonably retain the claim. If the amount is large, there is no corroboration at all, and the nature of the expense would be hard to explain, it may be prudent to remove it to avoid a larger problem in a compliance check.

If you are ever subject to a compliance check, HMRC will look at the overall credibility of your records. A few missing receipts for small amounts are unlikely to cause serious problems if your records are otherwise thorough and well-organised. For more on what a compliance check involves, see our guide on HMRC compliance enquiries after MTD filing.

A Quick Reference: Expense Types and What Proof to Keep

If you are uncertain whether a specific expense is allowable at all - before worrying about what proof to keep - our post on self-employed business expenses in MTD covers what you can actually claim.

How Long You Must Keep Everything

For most people under MTD, the rule is to keep records for at least five years after the 31 January filing deadline for the relevant tax year. So for the 2026-27 tax year (quarterly updates starting April 2026), you need to keep supporting evidence until at least 31 January 2033.

If HMRC opens a formal investigation, they can look further back in some circumstances - up to twenty years in cases of deliberate non-compliance. That is an extreme situation, but it is worth knowing. For the full breakdown of retention rules, see our post on how long to keep MTD records after filing.

Store and Submit Your MTD Evidence in One Place

AffordableMTD lets you import your expenses by CSV, attach supporting documents, and submit your quarterly updates directly to HMRC - no accounting knowledge required. If you're filing yourself and want a straightforward way to keep your records and submissions in order, try it free.

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Keeping It Manageable

The evidence requirements for MTD are not complicated, but they do require consistency. The filers who struggle are not those with complex businesses - they are those who let their records slide for a few months and then face a frantic catch-up before a deadline. A simple habit of photographing receipts, filing them by quarter, and doing a monthly sense-check against your bank statement will protect you from almost any compliance question HMRC might raise.

If you want to get your overall record-keeping approach right from the beginning, our practical guide to setting up your MTD bookkeeping system is a good place to start. And if you've already filed a quarter and want to check your records are in shape for what comes next, see preparing your records after Q1 filing.