How do I process a voucher created from a contract with retention in PS AP 9.1?

I have a contract with a 5% retention in every payment. Created a req for the contract; source it to a PO that shows the contract; budget checked, approved and dispatched. I  use a regular voucher into which I copy the PO for $5000.00 and Save: the voucher only generates a single payment line for $5000. Where is the split payment? I budget checked and submitted for approval. As per PeopleBooks "When a voucher is created from a contract with retention rules defined, the payment amount is split on the voucher. The retained amount is placed on hold, while the remainder is scheduled for payment by the PeopleSoft Payables Batch Voucher process".