So what actually is a CT600?
It's a form. The "CT600" is the name HMRC gives to the Company Tax Return that every active limited company fills in once a year. On it you put how much profit your company made and how much Corporation Tax that comes to. Think of it as your company telling HMRC, in HMRC's own words, "here's what we earned and here's the tax on it."
You don't fill it in by hand box by box. A tool like ours builds it from your year's figures and sends it in the format HMRC accepts. The form is the same one every UK company uses.
What goes with it?
This is the part people miss. The CT600 form on its own isn't a full return. Three things go to HMRC together:
- The CT600 form itself, with your profit and your tax.
- Your accounts, the summary of the money your company took in and spent over the year.
- The working, a short set of sums that shows HMRC how you got from your accounts to the tax figure.
The accounts and the working go in a digital format HMRC can read automatically. You never have to make that format yourself, the software does it. We turn your bank figures into all three pieces and send them as one return.
How is the CT600 different from the accounts I file at Companies House?
Most limited companies have two separate yearly jobs, sent to two different places:
| What | Where it goes | What it's for |
|---|---|---|
| Accounts | Companies House | The public record of your company's figures |
| Company Tax Return (CT600) | HMRC | Working out and paying your Corporation Tax |
The accounts that go to Companies House are on the public register that anyone can look up. The CT600 goes to HMRC and is about your tax. They cover the same year and share a lot of the same numbers, which is why people mix them up, but they are two jobs to two bodies.
There used to be a free government service that did both at once. It has closed, so to file yourself you now use software like ours. We send the accounts to Companies House and the CT600 to HMRC for you, in one go.
Do I need to send one?
If your company is active, the answer is almost certainly yes. HMRC sends you a letter called a "notice to deliver a Company Tax Return", usually once your company starts trading, and that letter is your cue to file.
You still send a return even if:
- your company made a loss, or
- your company earned nothing, or
- you owe no tax at all.
A company that genuinely did nothing all year usually files as dormant instead, which is a lighter version. If you're not sure which camp you're in, that's the first thing we work out with you.
When is it due?
There are two different dates, and the one for paying comes first:
- Pay your Corporation Tax: usually 9 months and 1 day after your accounting year ends.
- Send the CT600: 12 months after your accounting year ends.
So you pay the tax before you file the return. If your year ends on 31 March, you'd normally pay by the following 1 January and file by the following 31 March. Miss the filing date and HMRC charges a penalty that starts at £200, even if you owe no tax, so the dates matter.
Your first year works a little differently, because a new company's clock starts on the day it was set up. The first set of accounts often covers a longer stretch than a normal year, and that can even mean two tax returns for the one first period. Don't worry about any of that: we work your exact dates out for you and handle whatever your first year needs.
How SimpleReturns handles it
Connect your bank or upload a statement, and we build your CT600, your accounts and the working behind them, show you every figure to check, then send the accounts to Companies House and the CT600 to HMRC. You don't fill in a single box or learn a single tax rule.