One sum is enough. Most people enter the purchased sum as a cost line on the contract, and we recommend starting there.
How to do it
Go to Purchasing and create the contract.
Enter the purchased sum in the Cost column on the cost line, with the right production code.
Save.
Want to follow up per item?
The contract has a separate Estimate tab for estimate items, with item, resource, production code, unit, quantity and unit cost, among other things.
If you have the items in Excel, AIMZ can help you import them at item level. Get in touch via the chat.
You can start with one sum and add item level later.
Good to know
Several purchases can be on the same production code if different suppliers share the work.

