Invitation for Bid (IFB)
A formal solicitation document, most common on public and government projects, that invites contractors to submit a priced bid against a defined set of plans and specs, usually the strictest procurement method, where the contract has to go to the lowest responsive and responsible bidder rather than whichever proposal looks best overall.
Why it matters
Which procurement document an owner uses changes the rules of the game entirely. An IFB is price-driven and rule-bound by design (public agencies use it partly to avoid favoritism), while an RFP leaves room to weigh qualifications and approach, so a contractor has to respond completely differently depending on which one lands on their desk.
On a real project
A city issues an IFB for a new fire station, spelling out exact plans, specs, and bid-opening procedures. Bids are opened publicly at a set time, and by law the contract goes to the lowest bidder who meets the stated qualifications; the city can't choose a higher bidder just because it likes their team better.
Who this matters most to
An Estimator treats an IFB response as strictly price-driven; there's little room to sell qualifications or propose alternatives, so the number has to be right the first time. A Contracts Administrator makes sure the bid is submitted exactly to the IFB's procedural requirements, since a public agency can legally disqualify a low bid over a technicality like a missing signature or a late submission.
Where this goes wrong
A contractor submits the technically lowest bid on a public IFB but leaves out one required bid form. The agency disqualifies the bid on that technicality alone, awarding the contract to the next-lowest bidder, a costly reminder that on an IFB, being cheapest isn't enough if the submission itself doesn't follow the rules exactly.