Tax - What to Do When HMRC Says Your CT603 Notice Is Not in Their System | Clear Books Tax Support

What to Do When HMRC Says Your CT603 Notice Is Not in Their System

If you have received what appears to be a Notice to Deliver a Company Tax Return (form CT603) from HMRC, but HMRC's online system shows no record of that obligation, there are a few likely explanations.

Why HMRC's System May Not Match Your Letter

The letter may be fraudulent

HMRC phishing letters and scam correspondence are unfortunately common. Before assuming there is a legitimate obligation, verify the letter is genuine:

  • Check the reference number on the letter against your HMRC business Government Gateway account under Corporation Tax
  • Call HMRC Corporation Tax on 0300 200 3410 with your company UTR to confirm
  • Genuine HMRC letters will have a UTR, reference number, and specific accounting period dates
If HMRC confirms there is no matching obligation, treat the letter with caution and report it to HMRC's phishing team at phishing@hmrc.gov.uk.

The obligation has not appeared yet

If you have recently changed your accounting reference date (ARD) via Companies House, there can be a delay before HMRC's online system reflects the new obligation. HMRC typically issues a new CT603 within a few weeks of being notified of the change — but their online account can lag behind posted notices.

In this case:

  1. Wait a few days and check your Government Gateway account again
  2. Once the obligation appears, Clear Books Tax will pick it up after the ARD change processes through Companies House
  3. If it still does not appear after a week or two, contact HMRC to confirm

The period dates may differ

HMRC's Notice to Deliver may show different period dates than what Clear Books Tax expects from Companies House. If HMRC confirms the obligation exists but it is not showing in Clear Books Tax, see Filing a CT600 When Your HMRC Period Differs from Companies House.

What to Do

  1. Verify the letter is genuine — Call HMRC on 0300 200 3410 with your UTR and ask them to confirm the obligation and its exact period dates
  2. Get a reference number — If HMRC confirms the obligation exists, ask for a reference and the exact start and end dates
  3. Check your Government Gateway — Log in under Corporation Tax to see what periods HMRC has on record for your company
  4. Contact support — Once HMRC has confirmed the obligation and dates, we can help you file for the correct period
Until HMRC's system shows the obligation and any relevant ARD change has been processed through Companies House, Clear Books Tax cannot create the filing period automatically.

Was this guide helpful?