What is an invitation for bid (IFB)?

An invitation for bid (IFB) works as a price contest on fixed terms, with every supplier answering the same specification on the same form. The term belongs to formal public buying, where US state buyers issue documents headed invitation for bid and UN agencies call the same formal solicitation an invitation to bid (ITB). It leaves a supplier little to decide beyond whether it can meet each requirement and what it will charge.

How an invitation for bid works

An IFB fixes everything except the price. The buyer writes the requirement and the contract terms, and each supplier prices them on the buyer's own form, signs the bid and seals it.

Take a public buyer that needs a supply of office chairs built to a stated design. Its pack runs across several documents. The specification describes each item, the quantity needed and the standard it must meet. The bid form, with its price schedule, is where a supplier writes a price against each line and signs. The instructions to bidders say how to complete and deliver the bid, and the contract terms are the ones the winner will sign. Some packs also ask for a tender guarantee to be lodged with the bid.

Those terms belong to the buyer. A 2024 invitation to bid from the International Organization for Migration asks bidders to bid in line with the general conditions of contract and the schedule of requirements set out in the document itself. Those general conditions are the buyer's contract terms, not the bidder's. A supplier answering the chair IFB doesn't send its usual quotation or its own terms of sale. It checks that its chair matches each line, writes its prices into the buyer's schedule, signs where the form asks and seals the whole bid.

Sealing matters because every bid stays closed until a set moment. A 2025 IFB for translation services from a US state office required all bids under sealed cover, with a final submission date of 17 April 2025 and a bid opening on 23 April 2025. At the opening the buyer unseals the bids together, so no supplier can see a rival's price before it commits to its own.

How bids are judged

An IFB bid has to pass two checks before its price counts. The bid must be responsive, meaning it meets every requirement in the buyer's documents in the form they ask for, and the bidder must be responsible, meaning it is able to deliver the contract.

Responsiveness is judged on the bid exactly as it was submitted. In a 2025 invitation to bid for goods from UNESCO, a bid that is not substantially responsive is rejected, and the bidder can't make it responsive afterwards by correcting the non-conformity. That follows from sealed bidding itself. Once prices are open, letting one bidder repair its bid would let it change its offer after seeing everyone else's.

The test is whether the bid conforms in substance to the specification the buyer has already fixed.

Responsibility looks at the bidder rather than the bid. It asks whether this supplier can actually deliver what it has priced.

Price decides only among the bids that clear both checks. A 2025 IFB from a US state transport department states that the buyer identifies the lowest-priced bidder that meets the responsibility and responsiveness requirements. Another, from a US state health department, sought one responsive and responsible bidder offering the lowest total monthly net price. A cheaper bid that fails either check doesn't win.

When a buyer issues an invitation for bid

A buyer issues an IFB when it can specify exactly what it needs and is content to let price decide between suppliers who meet that specification. That usually means a requirement with a standard description, where one compliant offer serves the buyer as well as another and the remaining difference is cost.

Value plays a part too. The United Nations Global Marketplace (UNGM) describes the invitation to bid in the UN system as a formal, higher-value solicitation where the lowest price decides. It puts the usual threshold above 50,000 US dollars, though this varies between UN agencies. Below it, UN buyers turn to a less formal request, set out in the next section.

The choice of an IFB tells a supplier what kind of competition it is in before it reads the detail. There is no approach to propose and no quality score to earn, so the response is judged on compliance first and price second. That shapes the bid/no-bid decision, a supplier's call on whether a tender is worth the effort. The question becomes whether it can meet every line of the specification and still price competitively. An IFB sits in the same wider tender process as other invitations, from reading the pack to submitting the response, but with fewer judgement calls along the way.

How an IFB differs from an RFP, an RFQ and an ITT

An IFB differs from the other three in how formal it is and in how the buyer picks the winner. Where exactly the lines fall turns on the rules the buyer's procurement runs under.

Request for proposal (RFP)

A request for proposal (RFP) is used where a requirement can be met in various ways. UNGM's guidance says the best overall solution wins the contract, not necessarily the lowest price. An IFB fixes the solution and compares prices, while an RFP asks suppliers to propose the solution and compares the proposals.

Request for quotation (RFQ)

A request for quotation (RFQ) also asks for prices, but it is the less formal, lower-value sibling of the invitation to bid. Above the UN value threshold, the same kind of priced purchase usually moves to the formal IFB route.

Invitation to tender (ITT)

An invitation to tender (ITT) is the invitation a tender answers, tender being the word European buyers use for a formal bid. In UK public procurement it is the formal scored stage. It often follows a pre-qualification questionnaire (PQQ) or selection questionnaire, which screens suppliers before the main bid. An ITT typically asks for written answers that the buyer scores against its award criteria, the published basis on which it compares responses. An IFB has no scored stage of that kind. Compliance is pass or fail, and among compliant bids from capable bidders, price decides.