First VAT return after Sage upgrade

I upgraded my Sage version several weeks ago, and am now trying to do my first VAT return. Having done the journals, I know what my VAT liability is. However, when I run the VAT return calculation in Sage it does not match up.

I checked, and the sales tax and purchase tax figures are out by the original respective opening balance figures entered when I transferred to the new version (I transferred mid-way through a VAT cycle, but right after my financial year end – so my P&L was clear).

Please can you advise how I correct this – do I need to make adjustments on the VAT screen? If so, how do I adjust the following four figures (I do not make sales to the EC):

Tax due on sales

Tax due on purchases

Value of sales (excl. VAT)

Value of purchase (excl. VAT)

Thank you.