To prevent inconsistent data the application has multiple fail safes to prevent users from deleting records that are currently in use.
Foreign Key Constraint prevents a users from deleting a record that is currently in use.
A Supplier Contract has a required Contract Type and in order to prevent a Supplier Contract from being with out a Contract Type the application will prevent the user from delete the Contract Type that is currently used by a Supplier Contract.
Paid Vouchers and Invoices cannot be modified or deleted to prevent the loss of important finalized documents.
Contract, Vouchers, and Invoices may not be deleted after leaving the Draft status.