What happens automatically
When you incorporate at Companies House, HMRC is notified automatically and sets the company up for Corporation Tax. Within a few weeks, HMRC posts the company’s UTR (Unique Taxpayer Reference) to your registered office.
Keep that letter — the 10-digit UTR is needed for every Corporation Tax filing the company ever makes.
What you must do yourself
Within 3 months of starting business activity — trading, buying, selling, employing, advertising or earning interest — you must tell HMRC the company is active. You do this through HMRC online services using your Government Gateway account.
If the company is not yet doing anything, you can instead tell HMRC it is dormant, and no return is normally required until it becomes active.
After registration
HMRC will tell you your accounting period and the deadline for your first Company Tax Return.
When the time comes, OneFiler prepares and files the return, computation and accounts from your figures — see our checklist guide for what to have ready.