1. Receive payment from the customer and leave balance as underpayment.
   1. From the Customer menu, choose Receive Payments.
   2. Select the customer/job.
   3. Choose the invoice and enter the amount that the customer is paying.
   4. Select Leave as Underpayment.
   5. Click Save & Close.
      
2. Create a clearing account.
   1. From the Lists menu, select Chart of Accounts.
   2. Click the Account drop-down and select New.
   3. Choose Income as account type and select Continue.
   4. Use Clearing as account name and choose Save & Close.
3. Create two journal entries to move customer balance to your vendor.
   1. From the Company menu, select Make General Journal Entries.
   2. Assign Date and Entry No. if necessary.
   3. The first journal should be Credit to Accounts Receivable and Debit to Clearing account. Make sure to select the right customer in Accounts Receivable line.
      
   4. The second journal should be Debit to Accounts Payable and Credit to Clearing account. Make sure to select the right vendor in Accounts Payable line.
      
4. Apply credit to vendor's bill.
   1. From the Vendors menu, select Pay Bills.
   2. Select the appropriate vendor and bill.
   3. Click Set Credits
      
   4. Select the appropriate credit and click Done.
      
      Note: The credit shows in the Credits Used column. (If there is a remaining balance, you can enter the amount you need to pay in the Amt. to Pay field.
   5. Select Pay Selected Bills.