1.On the Vendor Bill click Credit
2. On the New Bill Credit Screen in the main field Amount enter the amount of your choice.
3. Under the Items tab > Items sub tab>for the line item, change the Rate to '0' and enter the same amount as in step 2 in the Amount field.
4. Under Items > Apply sub tab> enter the same amount as in step one in the Payment field.
5. Click Save.