Job costing
Materials, labor, subcontract and overhead roll up to the job as the work happens, against the estimate on the work order. Margin is visible before the job closes and after it bills, and a job that runs over shows which category moved rather than just a worse number at the end.
Inventory
Stock by location, by bin, by van. Counts reconcile against receipts and issues, so a variance points at a transaction instead of at a person.
Work orders
Schedule the job, track it to completion, bill it when it is done. Recurring service generates itself on the cycle you set.
Audit trail
Every change carries who made it, when, and against which record. The history is written as it happens, not reconstructed afterward.