Difference in VAT paid

You have to revise the returns of those months in which difference is found

The last date of filing revised returns in 31st december

After revising ur returns only, u can fill form 704 (Vat audit report)

U are supposed to pay the difference in vat or can claim refund/carry forward as per the case may be.

If u don't revise the return, u might get a notice from the sales tax authorities regarding the wrong calculation of vat payable and if u revise after the due date, interest/penalty shall be imposed.

Changes usually come when retention is not take during filing of original returns

Retention is the decrease in eligible set-off of various "other than machinery assets"