Credit memo or sub credit for wrong quantity in invoice

Question

hi,
vendor invoice printed wrong quantity.
po $10 * 10 = $100
migo - dr stock $100
         cr grc      $100
when receive invoice, additional 2 unit.
iv $10 * 12 = $120
in miro, i should not change the quantity as it will affect grc account.
miro - dr grc                      $100
         dr clearing acc           $20
         cr vendor                 $120
1 when vendor send in credit note of $10 * 2 = $20, should i create credit memo or subsequent credit?      
2 how is the accounting entry like?
thanks

Answer 1

1) You have to enter the subsequent credit
2) The account postings for a subsequent debit/credit depend on the quantity that the subsequent debit/credit applies to:
If the quantity of the subsequent debit/credit is smaller than or the same as the quantity delivered, the system tries to post the subsequent debit/credit to the stock account. If the material is valuated with a standard price or if there is insufficient stock coverage for the quantity to be debited or credited, the amount is posted to a price difference account.
If the quantity of the subsequent debit/credit is larger than the quantity delivered, the system distributes the relevant amount proportionally. The part of the subsequent debit/credit that does not have a goods receipt is posted to the GR/IR clearing account. The remaining amount is posted to the stock account u2013 or in the case of standard price control or insufficient stock coverage u2013 to a price difference account.