Sub-Contractor Booking and Cost Capture

Review the confirmed job and works order to identify all sub-contractor tasks, required dates, and estimated cost.

Contact the sub-contractor and confirm the day rate or fixed price, estimated duration, and any additional cost items in writing before booking.

Create a purchase order for the agreed sub-contractor cost referencing the job number. No booking proceeds without a PO.

Send the sub-contractor a written confirmation with job address, scope, start date, access details, and the PO number to quote on their invoice.

Record the sub-contractor's scheduled dates, contact details, and specific deliverable on the internal works order.

Obtain written sign-off from the site supervisor confirming the sub-contractor's work is complete before they leave site.

When the sub-contractor invoice arrives, match it against the purchase order: amount, job reference, and any unapproved additional charges.

Record the approved cost against the job. Only raise the customer invoice once all sub-contractor costs for the job are confirmed and captured.

Sub-contractors invoice for more than the agreed rate or add charges without prior approval, and without a written PO there is no document to dispute against.

Sub-contractor costs arrive after the customer invoice has already been raised, compressing job margin or creating losses that are not visible until weeks later.

Invoices arrive with no job reference, making it impossible to match costs to the correct job without manual tracking across multiple open projects.

Do I need a purchase order for every sub-contractor booking?

Yes. Even for sub-contractors you use regularly, a job-specific purchase order creates a record of the agreed cost, links the cost to the correct job, and gives you a document to match against when the invoice arrives. Verbal-only bookings regularly result in invoice disputes or unmatched costs that compress job margin.

What should a written sub-contractor booking confirmation include?

At minimum: the job address, a description of the scope of work, the agreed start date, access arrangements, your purchase order number, and confirmation of the agreed rate or fixed price. Send it by email so there is a timestamped record both parties can refer back to.