A new business has several HMRC deadlines in its first months: registering for Self Assessment by 5 October after the first tax year, telling HMRC within 3 months that a company has become active for Corporation Tax, registering for VAT within 30 days of the end of the month turnover passes £90,000, and registering as an employer before the first payday. Missing them can lead to penalties and HMRC questions later.

What are the registration deadlines for a new business?

  • Self Assessment. GOV.UK says you must tell HMRC by 5 October after the end of the tax year in which you started, for example by 5 October 2026 for the 2025 to 2026 tax year, or you could get a penalty.
  • Corporation Tax. GOV.UK says you must tell HMRC within 3 months of the start of your accounting period if your company is within the charge to Corporation Tax and is now active. See Corporation Tax deadlines.
  • VAT. You must register if taxable turnover over the last 12 months goes over £90,000, within 30 days of the end of the month you went over. You must also register if you expect to go over £90,000 in the next 30 days alone. See the VAT registration threshold.
  • PAYE. You must register as an employer before the first payday, and not more than 2 months before you start paying people. This applies to a sole director paid through payroll too.

What happens if a new business registers late?

Failing to tell HMRC you are liable to tax can lead to a failure to notify penalty, which depends on whether the failure was deliberate and whether you told HMRC before it found out. For a non deliberate failure disclosed within 12 months of the tax being due, an unprompted disclosure can reduce the penalty to nothing. See failure to notify penalties.

What should a new business get right?

Areas worth getting right in early returns include:

HMRC normally has 12 months from when a return is filed on time to open an enquiry.

Is tax investigation insurance worth it in the first year?

Cover only responds to checks HMRC opens after it starts, so the earlier it is in place, the more it protects. New owners are often least able to absorb an unexpected accountant’s bill. Read is tax investigation insurance worth it.

Tax investigation insurance pays your accountant’s fees if HMRC opens a check after your cover starts. Solar Protect cover pays up to £100,000 with no excess. It never pays tax, interest or penalties. Directors and partners can be included. Read how our cover works or get a quote today.

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 7 October 2026. Sources: GOV.UK guidance on registering for Self Assessment, Corporation Tax, VAT and PAYE. Cover is subject to the policy terms, conditions and exclusions. This guide is general information, not personalised tax advice.