Amending Vat Return

I am having to get a vat return to agree to a previously submitted return from another accounting system
I have found an error and amended it but it’s still showing on the vat return calculation
The Vat calculation shows a credit received was posted as a prepayment so I deleted the entry and put it in again against the correct invoice but it still shows as a prepayment on the vat calculation

It’s probably best if I can get some details here. I’ll send you a PM.