Troubleshooting HMRC errors

VATflow talks to HMRC on your behalf. When something stops that, the page says what happened in plain words and, where HMRC gave one, shows HMRC’s own code in brackets. Most problems fall into four groups: your connection to HMRC, your account’s security step, the figures or the file, and HMRC’s service itself. Each group below lists the messages, the usual cause and the fix.

• HMRC rejected our request. Please reconnect HMRC. The authority the business gave VATflow has expired (after 18 months), was withdrawn in the HMRC online account, or the Government Gateway account used is not enrolled for this VRN. Fix: Companies, then Reconnect HMRC, and sign in with the right Government Gateway account. See Add your company and connect to HMRC.
• CLIENT_OR_AGENT_NOT_AUTHORISED. HMRC’s code for the same thing: the signed-in Government Gateway user is not authorised for this VRN. Check the VRN and the account; agents also need the client’s authorisation.
• INVALID_VRN or VRN_INVALID. The VRN is not nine digits or fails HMRC’s check. Compare it with the VAT certificate and edit the company.
• NOT_FOUND. HMRC has nothing for this VRN and period: the period is not one HMRC expects, or the business is not signed up for Making Tax Digital for VAT. Check the VAT Returns list and the HMRC online account.
• This company is not connected to HMRC. Connect it from Companies before opening returns or payments.

• Confirm with your authenticator. Not an error: HMRC-reaching actions need a code from your app once per sign-in, and a fresh one for a submission. Enter the 6-digit code. See MFA and account security.
• Set up an authenticator app first. The account has no authenticator yet. Settings, Two-factor authentication, Authenticator app.
• Browser window larger than the screen. HMRC requires VATflow to report your screen and window sizes, and refuses a window that is bigger than the screen it is on, which happens with some multi-monitor set-ups and browser zoom levels. Fix: set the browser zoom to 100%, move the window fully onto one screen, and try again.
• Fraud prevention headers missing. A browser extension or privacy setting is stripping the information HMRC requires with every request (the Gov-Client headers). Try a different browser or disable the extension for VATflow.

• This period is not an open VAT obligation. The period was already submitted, or HMRC does not list it as open. The VAT Returns page shows the live list; a submitted period shows its receipt.
• This return has already been submitted. VATflow holds a receipt for this period and will not send it twice. Open the receipt from VAT Returns. HMRC’s own version of this message is DUPLICATE_SUBMISSION.
• Some box values are not valid, cannot be negative,more than two decimal places, must be whole pounds, above the maximum HMRC accepts. Fix the figure in your records or your file and re-import. The rules are listed in Preparing and submitting a return.
• A date is outside the period. A transaction line is dated before the period started or after it ended. Move it to the right period.
• That file is too large, could not be read, file type not supported. See the upload errors in Bridging.
• This import is locked. The period has been submitted, so its records can no longer change. Corrections go on the next return.
• TAX_PERIOD_NOT_ENDED. HMRC will not accept a return for a period that has not finished yet. Wait until the period end date.

• HMRC service temporarily unavailable (status 503), or SERVER_ERROR, or Could not reach HMRC. The problem is on HMRC’s side or between the two services. Nothing was submitted: a return is only recorded when HMRC returns a receipt. Wait a few minutes and try again.
• Planned maintenance and incidents are listed on HMRC’s page: HMRC service availability and issues (opens GOV.UK).
• If the deadline is close and HMRC stays unavailable, keep trying; HMRC publishes guidance on reasonable excuse for late returns caused by its own outages.

Please wait a few seconds and try again. VATflow limits how often one account can hit HMRC-reaching pages, to protect both services. The message tells you how long to wait. Refreshing repeatedly makes it longer.

Email support@vatflow.uk with the company name, the period, the exact message and, if shown, the HMRC correlation ID from the receipt or error. We reply within 2 working days. Never include your Government Gateway password or your authenticator codes.