External partie type: either an Circuit provider or Contract Service provider.
Accounting dimensions: Will be copied to each invoice. Although this this field is still available the use invoice templates with accounting dimensions should be prefered.
Monthly / Yearly recuring costs: Only one of these two options can be used for each contract. The value will be used, along with the invoice frequency, to calculate each invoice amount.
Invoice frequency : The number of month that each invoice covers.
Parent: Contrats can be arranged in a parent / child hierarchie.
