The activation code is the step between having a Government Gateway account and being able to file a corporation tax return with it. HMRC posts it, which is the source of nearly every problem with it: it takes days, it goes to the registered office, and it expires, and companies discover all three in the week the return is due.
What it is and how it arrives
After adding Corporation Tax to a Government Gateway account, HMRC sends an activation code by post to the company's registered office address. It normally takes about a week within the United Kingdom and longer overseas. Until the code is entered the service is added to the account but not usable, so the company can see the option and cannot file. The code is single use and tied to that account and that service.
When it expires or does not arrive
The code expires if it is not used, and a new one can be requested from the same account, which starts the postal wait again. The commonest reason a code does not arrive is that the registered office address on record is out of date, typically an old accountant's office, so a company that has changed advisers should check the address before requesting a code rather than after waiting for it. Requesting a second code invalidates the first, so a code that turns up later cannot be used.
What to do about the deadline
The deadline does not move because the code has not arrived. If the return is close, the practical answer is to have an agent file it: an agent authorised for the company can submit through their own credentials without the company's activation code, which is one reason companies with tight timing engage a firm for the year in question. Paying is separate and needs no code at all, so a company waiting on activation should still pay on time.
Questions people ask about corporation tax activation code
How long does a corporation tax activation code take?
HMRC posts it to the registered office and it normally takes about a week in the UK, longer overseas. The service cannot be used until it is entered.
What if the activation code expires?
Request a new one from the same account, which restarts the postal wait. Requesting a new code invalidates the previous one, so an old code arriving later will not work.
Can I file without it?
Not from the company's own account, but an authorised agent can file using their own credentials. Paying the tax needs no activation code.