For many self-employed borrowers, January isn’t just tax season, it’s the point where mortgage plans suddenly feel uncertain. Questions often arise around deadlines, income figures, and whether submitting a tax return could limit borrowing options.
One of the most important, and often misunderstood, factors is timing. When your tax return is submitted, and which tax year lenders use, can have a direct impact on how much you’re able to borrow.
Understanding this can help avoid unnecessary panic and ensure your self-employed mortgage application reflects your most up-to-date position.
The January 2026 Tax Return Deadline Explained
The deadline for submitting a self-assessment tax return for the 2024–2025 tax year is 31 January 2026.
For mortgage purposes, this means that:
- Income declared up to 5 April 2025 will be formally available to lenders once submitted
- Most lenders will rely on submitted tax calculations when assessing affordability
If profits in that tax year were lower than expected, it’s common for borrowers to worry that their borrowing potential has reduced, particularly if income has since improved.
What If Your Income Has Increased Since April 2025?
This is where timing becomes especially important.
If your profits have risen during the 2025–2026 tax year, those improved figures won’t automatically be reflected in a mortgage application until the next tax return is completed.
However, once the tax year ends on 5 April 2026, it is possible to:
- Submit your 2025–2026 tax return as early as April 2026
- Use the new tax calculation to evidence higher income
For some applicants, this allows lenders to assess affordability using more recent, and more favourable, figures.
This approach is particularly relevant for self-employed mortgage applications, where income trends can materially affect lender decisions.
Why This Can Increase Borrowing Potential
Many lenders assess self-employed income using:
- The latest available tax year, or
- An average of the most recent years
If the most recently submitted tax return shows increased profits, this can:
- Improve affordability calculations
- Offset a lower previous year
- Lead to higher borrowing capacity
For borrowers whose income is rising, waiting to submit the most up-to-date tax return, rather than relying on older figures, can make a meaningful difference.
This is especially relevant for sole traders and limited company directors whose income has grown since the 2024–2025 tax year.
When Waiting Makes Sense, and When It Doesn’t
Timing isn’t always about delaying an application. In some situations:
- A current mortgage deal may be ending
- A purchase may already be underway
- A lender may be comfortable using existing figures
In others, submitting an updated tax return at the earliest opportunity can help ensure income is assessed on the strongest possible basis.
This balance is often assessed when reviewing mortgages for the self-employed, particularly during tax season when figures are in flux.
How This Fits With Lender Income Assessment
Different lenders apply different rules around:
- Which tax year they accept
- Whether draft or finalised figures are required
- How income trends are treated
This means the same borrower can receive very different outcomes depending on how and when their income is presented.
During tax season, understanding these nuances often prevents unnecessary concern and helps ensure mortgage decisions are based on the most appropriate information.
What to Read Next
If income timing is a concern, the following topic builds directly on this:
This explains how income trends, increases, and decreases are treated across different lender types.
Discussing Timing Before You Apply
If you’re unsure whether submitting your tax return now, or waiting until figures are updated, could affect your mortgage options, discussing this before applying can help clarify the best route forward.
At Fox Davidson, timing and income presentation are considered carefully for self-employed clients, particularly during tax season when decisions feel more time-sensitive.
If you’d like to talk through your situation, please contact the team.
FAQs
How do mortgage lenders assess self-employed income in the UK?
Mortgage lenders usually assess self-employed income using figures from tax calculations. Sole traders are typically assessed on net profit, while limited company directors may be assessed on salary and dividends or share of company profit, depending on lender criteria.
Do lenders use gross or net profit for sole traders?
Most lenders use net profit, as shown on the tax calculation, rather than turnover or gross income. Net profit reflects income after allowable business expenses.
How do mortgage lenders assess limited company directors’ income?
Lenders may assess limited company directors using salary and dividends, salary plus share of net profit after tax, or, in some cases, salary plus share of profit before tax. The approach depends on the lender.
Will submitting my tax return reduce how much I can borrow?
Submitting a tax return does not automatically reduce borrowing potential. The impact depends on the figures submitted and how individual lenders assess income. Different lenders may reach different conclusions from the same tax documents.
Can lenders use retained profits for mortgage affordability?
Some lenders can consider retained profits when assessing limited company directors, particularly when income is structured to retain profits within the business rather than drawing them as dividends.
Is tax season a bad time to apply for a mortgage if I’m self-employed?
Tax season is not inherently a bad time to apply. However, it is a period when income figures are changing, so understanding how lenders will interpret those figures is particularly important.
