Managing taxes can feel stressful, especially when you’re dealing with different income sources as a director, contractor, landlord, or self-employed professional. The best way to stay in control is to understand the key HMRC deadlines that apply to the 2025/26 tax return.
This guide explains each important date in simple, easy-to-understand language so you can stay organised, avoid penalties, and plan ahead with confidence.
Every year, HMRC requires people with untaxed income to complete a Self-Assessment tax return. This includes income from side jobs, freelance work, contracting, property, dividends, or any earnings outside PAYE.
You must file if you are:
A company director
A contractor using your own limited company
A self-employed person earning £1,000 or more
A landlord receiving rental income
Someone earning dividends, investment income, crypto gains, or foreign income
Nothing major has changed, but HMRC continues to focus heavily on:
Correct reporting of dividends
Contractor compliance
Accurate digital recordkeeping
Clear reporting for multi-income individuals
Below is the full list of important dates you must keep in mind for the Self-Assessment return covering income from 6 April 2025 to 5 April 2026.
From this date, you are officially allowed to submit your tax return to HMRC.
Filing early is highly recommended because it:
Gives you more time
Helps you avoid last-minute pressure
Allows you to prepare for the tax bill ahead of January
Reduces the risk of mistakes
This deadline applies if this is your first year filing a tax return.
Even if you take a small PAYE salary, you still must declare your dividends, so most directors must register.
If you started freelancing or contracting any time in the 2025/26 tax year, you must also register by this date.
If you want to submit a paper tax form instead of filing online, this is your final deadline.
Most people now file online, but the paper option still exists.
If your tax bill is under £3,000, you can ask HMRC to collect it gradually through your PAYE tax code.
To use this option, your online return must be submitted by 30 December.
This is helpful for:
Directors on a small salary
Employees with side income
Anyone who wants smaller monthly deductions instead of a lump sum payment
This is the most important Self-Assessment deadline of the year.
By midnight on this date, you must:
File your 2025/26 tax return
Pay your tax bill
Make your first Payment on Account (if required)
Even if you owe no tax, filing late will still result in a £100 penalty.
Payments on account are advance payments towards your next tax bill.
You must pay this if your tax bill is over £1,000.
Many self-employed people and contractors are surprised by this because HMRC expects:
Your full tax bill
plus
50% of next year’s tax upfront
This is your second instalment towards next year’s tax.
Missing this payment leads to:
A 5% late payment penalty
Additional interest charges
This is one of the most commonly forgotten deadlines.
HMRC applies strict penalties to encourage timely filing and payment.
£100 immediately after you miss the deadline
£10 per day after 3 months (up to £900)
More penalties at 6 and 12 months
5% penalty after 30 days
Another 5% at 6 months
Another 5% at 12 months
Ongoing interest
These penalties can grow quickly, which is why early preparation is so important.
Preparing your Self-Assessment return is much easier when you collect all your documents early. At Spondoo UK, we require a clear set of records relating to your personal details, employment income, self-employment income, and any other untaxed income.
Below is a complete, easy-to-understand guide to everything you should prepare before filing.
Before we begin your Self-Assessment, please provide:
Unique Taxpayer Reference (UTR)
National Insurance (NI) number – usually found on payslips, P60s, or HMRC letters
Government Gateway login (if available)
These details ensure HMRC can correctly match your return to your account.
If you were employed at any point during the 2025/26 tax year, we’ll need:
P60 – summary of your annual income and tax paid
P45 – if you changed employers during the year
P11D – if you received benefits-in-kind that were not taxed through payroll
These records ensure we accurately report income already taxed through PAYE.
If you are self-employed, please prepare a full set of business records, including:
A summary of all business income and expenses
(spreadsheet, accounting software export, or bookkeeping system)
Business bank statements for the full tax year
Invoices and receipts for every sale and expense
Records of capital asset purchases, such as computers, tools, machinery or vehicles
Mileage logs or vehicle usage details if you use your car for business
Documentation for any grants or government support, including SEISS grants (if applicable)
These documents help us calculate your taxable profit correctly and maximise your allowable deductions.
You must also provide documentation for any income that hasn’t already been taxed, such as:
Dividends
Interest on savings or shares
Rental income from property
Foreign income
Investment income (including crypto)
Additionally, include:
Charity donations eligible for Gift Aid
Pension contributions that may qualify for tax relief
These are important because they can affect your final tax bill and available reliefs.
If you are a limited company director, you must provide:
Dividend vouchers for each payment made during the year
These confirm the amount received and support your tax return in case HMRC requests evidence.
Landlords must provide a full set of rental records, including:
Rental statements
Mortgage interest summaries
Repairs and maintenance receipts
Costs such as insurance, letting agent fees, and service charges
These records ensure your property profit is calculated accurately and fairly.
Apps and online software help you track income and expenses more easily.
Directors especially need accurate, organised records throughout the year.
Knowing your estimated tax bill early helps avoid cash-flow pressure in January and July.
Understanding Self-Assessment deadlines helps you stay in control, avoid HMRC penalties, and manage your finances with confidence. The 2025/26 tax year has several important dates, and planning early will save you stress later.
At Spondoo UK, we’re here to guide you through every step — from gathering documents to submitting your return on time.
Let Spondoo UK handle your Self-Assessment with expert care, accurate filing, and friendly support every step of the way. Click below to get started and secure stress-free tax compliance today.
