How the self-assessment deadline impacts getting a mortgage

Quick insights:

• The self-assessment deadline is 31st January

• Filing early is beneficial if you’re getting a mortgage

• Missing the tax return deadline can cost fees and delay your mortgage application

If you’re a sole trader, landlord, or limited company director, you likely already know that the deadline for filing online self-assessments is 31st January. In reality, you’re able to send in your self-assessment as soon as the tax year finishes, from 6th April, though many leave it late. But if you’re relying on this income for a self-employed mortgage, it’s wise to work it in early. 

How does the self-assessment deadline affect my mortgage application?

When applying for a mortgage as someone self-employed, freelancing, or contracting, proving your income is one of the major hurdles. You’ll be required to show proof of earnings, contracts, and tax returns. 

One piece of evidence you’ll need is the form SA302 – with most lenders looking for the most recent 2-3 years of SA302s to verify your income and determine your affordability. These forms can either boost your borrowing power or stall your application, and you can find out how to get your SA302 tax calculation here.

To receive your SA302 forms from HMRC, you must have completed and filed your self-assessment tax return. If you’re in the process of applying for a mortgage, then delaying in submitting your tax return will result in a delay in receiving the necessary forms from HMRC. This, in turn, slows down your mortgage approval. 

And if lenders see £100+ late filing penalties, it suggests you may be disorganised with your finances. On top of that, if you have a large HMRC debt to settle, it could eat into your immediate cash, such as your home deposit.

What happens if you miss the deadline?

If you miss the January self-assessment deadline, you may face an automatic £100 penalty, even if you owe no tax. Fines increase over time, and these fines and missed returns can hinder your mortgage application. Our advice? Aim to submit your tax return early or on time to avoid penalties. 

If you’re in the middle of getting a mortgage – or considering one – and you end up filing late, talk it through with your mortgage broker. It’s typically best practice to pay the HMRC debt in full (and prove it) before you can move forward with your mortgage.

Some high-street banks like to see returns filed by October to see a more up-to-date picture of your finances. 

Also note that as part of the Making Tax Digital initiative, starting in April 2026, HMRC is set to start gathering data every quarter from sole traders who expect to earn a gross income over £50,000. Whether you work with an accountant or manage your own books, staying on top of your digital records is more vital than ever. 

Getting a mortgage when self-employed

Proving your affordability is the most important step of getting a mortgage for someone self-employed. And on-time tax returns and SA302s can help. So can a mortgage broker.

At Mojo Mortgages, we offer free mortgage advice, comparing thousands of mortgages deals across a wide range of lenders. And, we’re by your side the whole way. We’ve supported freelancers, contractors, sole traders, and thousands more secure their mortgage deal.