Entry for sales return of exciseable goods

Dear/Madam,

i heve sale a materail (exciseable goods) about 600 kg. basic amount 100000/- excise duty(12.36%) 12360/- vat (2.75%) 3090/- on excise invoice

but party rejected some material(on excise invoice) about 20.40 kg. basic amount 3400/- excise duty 420/-, vat (6.05%) 231/- sending an excise invoice.

my question is how can i pass entry for this invoice(rejected material) whether i have to pass purchase entry or sale returns entry in the books of account. we have not any material on this rate of vat (6.05%) we have only one material at 2.75% vat rate.