Payment terms are an essential part of an agreement and should not be omitted or left to be decided until after the agreement is signed. Good drafting requires that the payment terms be clearly laid out in the agreement.
Avoid ambiguity as to what the amount owed will be, or provide a clear formula for determining the amount owed. Put terms that explicitly state how much is owed and when, and also throw in what will happen if the other party doesn’t pay or pays late. And, make sure to allocate who pays any taxes involved.