Addenda are issued during the bidding period to fix errors, clarify scope, answer pre-bid RFIs, or change the bid date. Each addendum is numbered (Addendum 1, Addendum 2, etc.) and must be acknowledged on the bid form.
Missing an addendum is a serious bidding error. Read every addendum carefully and update your takeoff to reflect changes. Plan revisions in addenda can shift quantities significantly — re-measure affected areas.
After bid, no more addenda. Changes after award become change orders.