How Do You Write a Bid Addendum?

A bid addendum is a written change to the bid documents issued before bids are due, so every bidder prices the same thing. A general contractor issues two kinds to its trade bidders: it passes on the owner's or architect's addenda to the drawings and specifications, and it writes its own for changes to a package, such as moving a scope item from one trade to another.

The federal rule for sealed bids sets the standard. Changes to quantity, specifications, delivery schedules or opening dates, or corrections to a defective or ambiguous invitation, are made by amendment, and "The fact that a change was mentioned at a pre-bid conference does not relieve the necessity for issuing an amendment." Amendments go, before bid opening, to everyone who received the invitation (FAR 14.208). A private GC is not bound by the FAR, but the same discipline keeps a bid fair and the bids comparable.

1. One change per item, numbered within the addendum (2-1, 2-2, 2-3), so bidders and you can refer to it later.
2. Name the exact place: Section 22 13 16, paragraph 2.3.B; sheet P-201. "See plumbing drawings" is not a location.
3. Use Add, Delete or Revise to read, and give the full new text. A bidder should not have to infer the result from the old text and a description.
4. Reissue changed sheets with a revision number and a cloud around each change. Narrative descriptions of a drawing change get read differently by different bidders.
5. When a scope item moves between packages, issue it to both. Moving firestopping to the plumbing package means a deduct for the firestopping bidders and an add for the plumbers.
6. Put price-affecting answers in the addendum, not only in a reply. If an answer changes what a bidder would price, it belongs here (see how to answer bidder questions).

The dates matter. This addendum goes out three days before bids are due, and item 2-1 adds equipment that needs a supplier quote. The federal rule asks the contracting officer to "consider the period of time remaining until bid opening and the need to extend this period" before amending (FAR 14.208). If bidders tell you three days is not enough to price the interceptors, move the bid date in the addendum itself, or issue a short one that does.

Federal bidders must acknowledge each amendment: by signing and returning it, by identifying the amendment number and date on the bid form, by letter, or by fax or email where those bids are allowed, and the acknowledgment must be received by the time and at the place set for bids (FAR 52.214-3). A missing acknowledgment can be waived as a minor informality only if the bid clearly shows the bidder received the amendment, or the amendment has no effect or merely a negligible effect on price, quantity, quality or delivery (FAR 14.405).

Private bids work best on the same terms. Ask for each addendum by number on the bid form. When a bid comes in without the latest one, it priced older documents: ask the bidder to confirm in writing, or price the difference as a plug when you level the bids. Never assume an unacknowledged addendum is included.

Addenda are usually the last step after the invitation to bid and the package's scope of work. Once the subcontract is signed, changes are no longer addenda; they go through a change order.

In Conflo, you issue a trade addendum from the Q&A and addenda tab of a trade bid, with a title and a description of what changed; Conflo numbers trade addenda in order on each trade bid. Once the trade bid is out, every bidder who has not declined and has an email address gets a short heads-up with the addendum number and title and a link, and acknowledges the addendum in Conflo. A bidder must acknowledge the latest trade addendum before submitting or updating a bid; one whose bid is already in is told the bid must cover it, and can still revise after the due date for that purpose only.

Under each addendum you see how many bidders have acknowledged it and who has not, with a Remind button for one bidder or all of them (at most one email per bidder per addendum a day). If a bidder confirms by phone or email instead, an approver on your team can mark it acknowledged manually with a note, which is kept on the record. Bids missing a trade addendum are flagged on the Bidders tab, and selecting one in leveling brings up a warning that an approver can override with a reason. Trade addenda can be issued until the package is awarded.

A good addendum is specific and complete: numbered, dated, one change per item at an exact location, revised sheets attached, the bid date stated, and an instruction to acknowledge it.

Send it to every invited bidder in time to price it, and check every bid for the acknowledgment. The bids that come back then price the same documents.

See how trade bids work in Conflo

1. FAR 14.208, Amendment of invitation for bids — Acquisition.gov, U.S. General Services Administration. Read October 22, 2026.
2. FAR 52.214-3, Amendments to Invitations for Bids — Acquisition.gov, U.S. General Services Administration. Read October 22, 2026.
3. FAR 14.405, Minor informalities or irregularities in bids — Acquisition.gov, U.S. General Services Administration. Read October 22, 2026.