You can add Contractors as Suppliers and add a write in. You can then send them a PO and receive the invoice.
1. To do this, go to Inventory → Suppliers and click on New.
2. Enter the necessary details like you normally do with supplier but this time, enter the contractor information such as name, address, etc.
Once done, click Save.
3. You can add a Write In and select the Contractor as Default Supplier and raise PO.
Access one of your jobs and to go Supplies tab and Add Write In.
4. Add the necessary details, tick the box beside Must Be Ordered and select the Contractor Name and once done, click Save.
5. Click Create Purchase Orders.
6. A PO gets generated and access it to view more details.
6. From the Purchase Order screen, you have the option to Email it to the contractor.