Hi,
As this is unplanned delivery costs & use t.code: OME2 and create new payment term as Z001 with 90% at the final phase and paying 10% of contract 2 months later.
During creation of service vendor master, enter new payment term Z001 & during transaction process of MIRO,based on vendor you will have payment term and post invoice.Now you can pay vendor 90% and later 10% as needed.
OR
During creation of service order creation, enter new payment term Z001 & during transaction process of MIRO,based on service order you will have payment term and post invoice.You can pay vendor 90% and later 10% as needed after 2months
Regards,
Biju K