Service

On Signing

Customer A/c. Dr
Service Contract Control A/c. Cr (Liability)

On Payment

Bank A/c. Dr
Customer A/c. Cr

Invoicing (Sale Price)

Service Contract Control A/c. Dr
Customer A/c Dr (VAT)
Service Sales A/c. Cr
Spare Part Sales A/c. Cr
VAT a/c Cr

On Invoicing (Cost price)

Cost of Goods Sold (Spare Parts) A/c. Dr
Material Consumed for Job Card A/c. Cr

Cost of Service (Labour) A/c. Dr
Labour Charges for Job Card A/c. Cr