Is there a deadline?
Yes. HMRC require your Company Tax Return within 12 months after the end of the accounting period – (although you have to pay your corporation tax 9 months and 1 day after your company year end, so in real terms you need to get your company tax return within 9 months of the year end. See the handy table below!)
Companies House require your annual accounts within 9 months of your year end.