Corporation Tax Return Filing Checklist for Businesses
Running a limited company in the UK comes with its fair share of responsibilities — and one of the most important is getting your Corporation Tax return right. It’s not just about paying what you owe; it’s about staying compliant, avoiding penalties, and making sure everything is submitted on time.
If you’re not sure where to start or just want to double-check your process, this practical checklist will walk you through what needs to be done to file Corporation Tax smoothly and correctly.
- Confirm Your Accounting Period
First things first: make sure you know your company’s Corporation Tax accounting period. For most companies, it matches the financial year, but there are exceptions — especially in your first year or if you’ve changed your accounting date.
You can check this via your HMRC business tax account. It’s important because your tax return and payment deadlines are based on this period.
- Get Your Statutory Accounts Ready
Before you can do anything with your tax return, you’ll need to put together your statutory accounts. These show your company’s financial activity for the year and are required by both Companies House and HMRC.
They should include your balance sheet, profit and loss account, and notes to the accounts. Depending on your company size, you might also need to include a director’s report and an auditor’s report.
- Adjust for Tax Purposes
Here’s where it gets a bit technical. Your taxable profit isn’t always the same as the profit shown in your accounts. Certain expenses might not be allowed for tax purposes — like client entertainment — and there may be other adjustments to make, such as adding back depreciation and claiming capital allowances.
You’ll also need to include things like R&D tax relief (if applicable) and any carried-forward losses.
- Complete the CT600 Form
The CT600 is your Corporation Tax return form. It includes sections on your company’s income, allowable expenses, tax adjustments, and reliefs. If your business structure is more complex — for example, if you have group companies or overseas operations — there are additional sections you might need to fill out.
If this part sounds daunting, you’re not alone — many businesses work with accountants or tax advisers to ensure accuracy.
- Submit Online to HMRC
Corporation Tax returns must be filed online — either through HMRC’s system or with approved commercial software. Paper returns are generally not accepted unless you have a valid reason.
The deadline for submitting your return is 12 months after the end of your accounting period, but don’t leave it too late. Remember, your payment is due earlier — usually 9 months and 1 day after your year-end.
- Pay What You Owe
Once you’ve calculated your Corporation Tax liability, the next step is to make sure the payment reaches HMRC on time. You can pay via bank transfer, Direct Debit, or through online banking. If you’re a larger company with profits over £1.5 million, you’ll likely need to pay in instalments.
Late payments can lead to interest and penalties, so it’s worth setting reminders.
- Keep Your Records in Order
HMRC can ask to see the records behind your tax return, so make sure you keep everything — invoices, receipts, bank statements, payroll details, loan agreements, and any correspondence — safe and accessible.
You should hold on to these for at least six years, just in case HMRC decides to take a closer look.
Get Help If You Need It
Corporation Tax can be complicated, especially if your business is growing or you have unusual transactions. Many companies choose to work with an accountant or tax adviser who can help prepare and file Corporation Tax on their behalf.
Not only does this take the stress out of the process, but it can also help you spot legitimate ways to reduce your tax bill.
