Again this is different if you are incorporated or not.
If you are self employed and file a tax return then your tax year runs from 6 April – 5th April. You will have to pay your tax (if due) by 31st January the following year otherwise HMRC will add 5% to your tax bill.
If you trade through a limited company then you must pay your corporation tax 9 months and 1 day after your accounting year end. This is normally three months before the deadline for filing a return with HMRC.