We run a website for our wholesale customers which allows them to place orders. The order is then passed to our accounts department for invoicing.

After a recent upgrade from v1.39h to v1.54 I've noticed odd discrepancies between what Zen Cart is charging for VAT and the invoices raised by our own system - for example, Zen Cart calculates VAT on an invoice of £83.92 as £16.78, however our accounts software calculates it at £16.81, because it calculates VAT per item, rather than on the total amount.

Before the upgrade Zen Cart would give the same VAT figure as our accounts software, so I can only assume the calculation has changed in between 1.39 and 1.54. Is there any way of changing this back - which file(s) should I be looking at?

Thanks in advance,
Lee