The interim trading program is optional functionality that can be used if an active trading program ends before a replacement trading program, or proposal, is activated. An interim trading program is a placeholder that allows the continued accrual of rebate earnings and optionally the allocation of cash. It is a locked trading program and can only be created by either manual or automatic replication of an active trading program to the next period. The activation of a proposal can be set to replace the corresponding interim trading program(s).
You can read more about interim trading programs here.