Vat and purchase issue

Manoj chopra (article) (128 Points)

31 December 2012  

I am Auditing a co. ,they are doing a accounting mistake For eg. Quotation for vat purchase is selected @ of RS. 10 but bill is recieved @ RS.12 Due to some software problem of the other party and payment is made @ RS. 10 only ....

In recording the above ,Purchase A/c -DR  Rs. 12

                                           VAT A/C-DR ( @ on RS. 12)

                                                 To Customer A/C-

THEN ,On the date of payment :-          Customer A/C -DR Rs.12

                                                                             To Bank A/c                      10

                                                                              To Rate difference A/c     2

Since by doing the above accounting they are wrongly recording the purchase ,i want them to clear there rate difference account but Since the Vat return has been filled so they cannot change there purchase figure since it is already filled in vat return .

Can nyone plz tell me the possible  solution of the above prob. ,and future solution of the above problem? plzzz tell ???