If you are setting up many trade allowance agreements then it might be handy to create a trade allowance agreement code which you can use to default in the dates for the promotion. Here you can specify the dates for order, receipt, ship and performance. Then when you create an agreement they will copy across.
Here is a quick overview.
D365 1611 Update5 (7.0.4475.35138)
AX2012 R3 CU11