In reality there are only two outcomes from a live transmission to HMRC.
The first is Success - your Vat Return submission has been accepted, this is confirmed by you being able to print out a hard copy of the Vat Return showing the date / time stamp accepted by the live HMRC servers along with uniquely identifiable markers.
Secondly, FAILED - your request for whatever reason failed, it will need to be redone, this could be various reasons such as;
Wrong Vat Number
No Client Authority
Data Details are incorrect
HMRC servers are too buys
If you receive the last error, simply give it 20 minutes and try again, sometimes coming to the last few days before the expiry date millions of people are trying to submit their returns and the servers are just too busy !