Starting a limited company is an exciting step, but being a company director also brings responsibilities. In your first year there are several deadlines and admin tasks to keep track of.
This checklist covers the key things to consider in your first year, including how to handle an extended first accounting period.
Your first-year checklist
- Keep your company details up to date. Tell Companies House about any changes to your registered office address, directors or people with significant control.
- Keep accurate accounting records. Record all income, expenses, assets and liabilities.
- Know your company tax return deadlines. The payment deadline comes before the return deadline (see below).
- Know your annual accounts deadline. Your first accounts are due earlier than you might expect.
- Prepare your first-year filings. If your first period is longer than 12 months, you will need two CT600 returns.
You will also need:
- Your Company UTR
- Your Government gateway details (username and password)
- to activate your corporation tax service
- your Companies House authentication code
Keep your company details up to date
When you register a limited company, you give Companies House your registered office address, directors and people with significant control.
If any of these details change, you must notify Companies House. Accurate information means official correspondence reaches you and your company's public record stays correct.
Keep accurate accounting records
Your company must keep a record of its income, expenses, assets and liabilities, along with any other financial transactions. These records form the basis of your company's annual accounts, so good record keeping makes your year-end filings far easier.
Key deadlines at a glance
| Filing | Deadline |
| Corporation Tax payment | 9 months and 1 day after the end of your accounting period |
| Company tax return (CT600) | 12 months after the end of your accounting period |
| First annual accounts (Companies House) | 21 months after your date of incorporation |
| Annual accounts in later years | 9 months after your company's financial year end |
The Corporation Tax payment is due earlier than the Corporation Tax return. Don't wait until the return deadline to pay, or you may face interest and penalties.
What do you need to file for your first year?
If your first accounting period is longer than 12 months, you will need to prepare:
- 2 x CT600 company tax returns
- 1 x iXBRL tagged set of annual accounts
- 1 x Companies House accounts submission
A CT600 can only cover a maximum of 12 months, so an extended first period has to be split across two returns. The first CT600 covers the first 12 months and the second covers the remainder. You should receive a notice to file a company tax return from HMRC. This will detail the dates that HMRC require your tax return to be made up to. It is usually from the date of incorporation to the last day of the month of incorporation in the following year.
Your first accounting period can differ from a standard 12-month year because your accounts and your CT600s can cover different periods:
- Accounts (iXBRL and Companies House) can cover the full extended period.
- Corporation Tax returns must be split so that neither covers more than 12 months.
Because the two CT600s cover different periods, you will need to apportion your financial figures between them.
Example
A company incorporated on 24/07/2024 could have a first accounting period of 24/07/2024 to 31/07/2025. This is how it would be filed:
| Filing | Period covered |
| First CT600 | 24/07/2024 – 23/07/2025 |
| Second CT600 | 24/07/2025 – 31/07/2025 |
| iXBRL tagged accounts | 24/07/2024 – 31/07/2025 |
| Companies House accounts | 24/07/2024 – 31/07/2025 |
How to complete your first-year filings
Using the example above, follow these steps to make sure your filings are completed correctly.
1. Set up your filings
Confirm the accounting period dates and your company size. You will need two CT600s and one set of accounts covering the full period.
2. Apportion your figures
Because the Corporation Tax period is split, your financial figures must be divided between the two returns:
- CT600 1: 24/07/2024 – 23/07/2025
- CT600 2: 24/07/2025 – 31/07/2025
3. Enter and check your financial information
Complete both company tax returns and the accounts with the relevant figures, and check them carefully before moving on to the final sections.
4. Set box 50 to "Yes" on both CT600s
This tells HMRC that more than one Corporation Tax return is being submitted for the overall accounting period.
5. Complete the declaration on the second CT600
On the declaration page of the second CT600:
Set box 80 to No
In box 90, indicate that the accounts were submitted with the separate return
You don't need to submit the same accounts again with the second CT600.
6. Submit to Companies House
Check that the correct iXBRL tagged accounts (24/07/2024 – 31/07/2025 in our example) are attached to your Companies House annual accounts submission.
