So what are my actual choices?
HMRC puts it in one sentence: you can get an accountant to prepare and file your tax return, or you can do it yourself.
Doing it yourself means using software. HMRC wants the return sent electronically through a commercial product, and the paper form only comes out in rare cases, such as filing in Welsh or having a genuine reason you could not file online.
So the question is not really "how do I submit it". It is "who presses send, and with which product".
Route one: an accountant or tax agent files it for you
You hand over your figures. They prepare the accounts and the tax return, they file both, and you approve what goes out. You need no filing software of your own, because they already have theirs.
This suits you if your company has anything unusual going on, if your year has been messy, or if you would rather pay someone to hold the whole thing. Our guide on when you actually need an accountant goes through the situations where that is the right call.
One point worth knowing before you assume it is handled: the return is still your company's return. Your accountant prepares and sends it, and your company stays responsible for what it says.
Route two: you file it yourself with recognised software
You buy or subscribe to a product that can build the return and send it to HMRC, and you press send. HMRC publishes a list of the software it works with, and it says it accepts returns filed using any of the products shown there.
Read that list carefully, because not every product on it can send a return. It is split into sections, and only the first section, headed "Produce and submit CT600", covers the products that actually build and submit the return. The other sections are for products that only prepare parts of your accounts in the format HMRC needs.
The genuinely useful part is in that first section, and most directors never notice it. Alongside each supplier there is a column headed "Suitable for self-filers". A "Yes" means a business can use it to file its own return. A "No" means it is built for accountants filing on behalf of clients. That one column answers the question the rest of this guide is about. If you want to know what "recognised" actually means before you shop, read what HMRC-recognised software really means.
What happened to HMRC's own free service?
It closed on 31 March 2026, so it is no longer a route for your company. We have written that up separately in the free HMRC filing service has closed, which covers what changed and what did not.
Why won't my accounting software file my tax return?
Plenty of directors pay every month for a well-known accounting package, keep their books tidy in it all year, and assume the Corporation Tax return comes out of the other end. Then they reach the deadline and find the filing button is not in their subscription.
The reason is product design, not quality. Some brands build one product for business owners doing their own books, and a second product for accountants in practice who file for dozens of clients. The tax return lives in the second one.
Xero is the clearest example we could verify. Xero's Corporation Tax filing sits in a product called Xero Tax, which Xero makes available only to advisers on its partner programme, at no extra cost to them. Xero has said so plainly on its own public forum, including "Xero Tax remains a Partner only product". You can see the same thing on HMRC's list, where Xero Tax is marked "No" in the self-filers column. So as things stand at the end of July 2026, a business owner with an ordinary Xero subscription cannot use it to send their own CT600, even though the same brand does their bookkeeping. Xero has also announced a separate paid yearly add-on for small businesses, due from August 2026, which it says will let a small company file micro company accounts and a Corporation Tax return from inside Xero. That is next month, so check whether it has landed and whether your company qualifies before you assume either way.
None of this makes Xero a bad product. It is a good product built for a different job than the one you are trying to do. Directors get caught out by assuming bookkeeping and tax filing come in the same box, so check yours.
Other products are built the other way round. FreeAgent, for example, lets a limited company file its own year-end accounts to Companies House and its Corporation Tax return to HMRC from inside the company's own account. It is built for micro-entities, which is most very small companies but not all of them, so check that yours fits. On HMRC's list it is marked "Yes" for self-filers, which is exactly the check we are telling you to make.
For the avoidance of doubt about who is writing this: we build one of those direct-to-business products too, and there are several others. Run the same check on us that you would run on anyone else, and ask us the three questions below in writing.
How do I check what my software can actually do?
Two neutral places to look, then three questions to ask.
The lists:
- HMRC's list of software for Company Tax Returns. Go to the "Produce and submit CT600" section and read the "Suitable for self-filers" column. "Yes" means a business can file with it itself. HMRC says it accepts returns filed using the products shown, but it does not recommend one over another.
- The Companies House software finder for your annual accounts, which is a separate filing to a separate place. Companies House does not recommend any product on it.
The self-filers column on HMRC's list is the closest thing to a straight answer you will find in one place, so start there. It still will not tell you which plan of a product you need, or what it costs, and the Companies House finder does not split products by who they are sold to at all. So use the lists to shortlist, then ask the supplier the three questions below.
The three questions to put to any product before you pay:
- Can I file the Corporation Tax return myself, on the plan I am buying, without an accountant's login?
- Does it also file my accounts to Companies House, or only the tax return? Those are two filings.
- Does it support my kind of company, including anything odd about my year?
Ask them in writing. A straight answer takes a supplier one line.
A worked example
Priya runs a small design company on her own. She pays £33 a month for a bookkeeping subscription, which comes to £396 a year, and her books are spotless. Eleven months after her year end, she goes looking for the button that sends her Corporation Tax return, and it is not there. Her plan does the bookkeeping. The tax return sits in the version her accountant would buy.
Her £396 is not wasted, and it is not refunded either. It buys the bookkeeping, and the filing is a separate cost on top whichever route she picks now. She has weeks, not months, to choose one and get it done. There is a sting she has not spotted yet, too: the deadline for paying a small company's Corporation Tax bill comes earlier than the deadline for sending the return, so at month eleven the payment is already late even though the return is not.
Our guide on what it costs to file yourself versus an accountant has the numbers for both.
Had Priya asked question one in month two instead of month eleven, she would have had a calm year, the same bill, and no late payment.
Which route is right for me?
Pick the accountant route if your company has moving parts you would rather not think about, if you want a person to ask questions of, or if the year has been complicated.
Pick the self-file route if your company is small and straightforward, your records are in decent shape, and you want to see and approve every figure yourself. We are one of the products built for that second group, and we are one of several. The honest comparison of both routes lays out the trade-offs without picking a winner for you.
Whichever you choose, choose it early. The worst version of this is discovering your route does not exist with a fortnight to go.