When an item is booked in for a repair, the process should be the same as a normal job, where the job is raised against the Customer and the associated Customer Item is added to the job.
Parts and labour are added to the job as used in the workshop.
Once the job is ready to be collected, advise the customer and then change the status of the job to “Pending Warranty Claim” and save the job
Complete the Warranty Claim with your Supplier.
Once you have received the confirmation from your Supplier, add a General Ledger ID to the job to remove the value coding it to the GL ID for the Warranty Expenses - Supplier
When the Credit is received from your Supplier, code this to the same GL ID.
The net result will show you that Supplier cost $160.52 in warranty repairs, they reimbursed you with $142.00 therefore there is a net cost to you of $18.52 for the period.