If you see an error message that looks a bit scary - don't panic! You can tap "more" to see some detail. A common problem is you might have got your Gov Gateway details wrong - HMRC refers to this as you "user credentials". Other errors might look more baffling - in which case you just need to look at the boxes ZapTax has placed in the error screen, so tep"OK" to do that. It's likely you just missed entering a figure in one of them. If a box doesn't apply to you, check that it's blank - if you entered "0" or "0.00" delete this and leave it blank. You can then try re-submitting. You're submission credit won't be used until you've successfully submitted and received an official receipt code from HMRC. If you're still not able to submit, raise a support ticket here on the ZapTax helpdesk or call 01702 463162.