I purchase different spares from different suppliers, do I have to manually enter discount for a customer every time I sell them something, or can I set a term in ?

Hello

Are you passing the cost on as a billable expense or creating an invoice when you get the order?

If  you are creating the invoice you can add a discount in that section,if you go to the cog in the top right,go to account and settings and sales and then in sales form content, if you then click into that section and then turn on discount and you will have a box on the invoice to add in discount

The terms only dictate when the invoice is paid(as in how many days they have to pay and you can add a discount if it is paid early)So the option above is the better option

Any questions let us know