Time off bidding is a structured process for allocating popular vacation periods in advance, using a published rule rather than whoever asks first. Employees submit ranked preferences during a bid window; the employer awards slots by seniority, rotation, lottery, or a hybrid of those; and the results are published before the leave year begins.

It’s also called vacation bidding, PTO bidding, or simply the vacation bid.

The problem it solves

Christmas week, the first week of July, and the school holidays are wanted by far more people than any roster can release at once. Under first-come, first-served, those weeks go to whoever reaches the request form fastest — which in practice means whoever was at a desk rather than on a shift, in the right time zone, and not on leave the morning the window opened.

That isn’t an allocation; it’s a reaction-time contest. Bidding replaces it with a rule everyone can see in advance.

How a bid round works

Most systems run in rounds.

In the primary round, employees submit ranked choices — commonly three to five acceptable periods rather than one. The employer applies the allocation rule, awards slots up to the coverage limit for each period, and publishes the results.

A secondary round then opens on what’s left, for anyone unawarded or who still has leave to place. Large or complex workforces may run several further rounds until capacity is allocated.

Bid windows come in two shapes. A concurrent window has everyone bid during the same period, with the ranking applied afterwards — so submitting first confers no advantage. A sequential window gives each employee an individual slot to choose in priority order.

Allocation methods

• Seniority. Priority by length of service. The most common method, and usually mandated where a collective agreement exists. Predictable and easy to defend — but the same people win the same weeks every year, which is exactly the complaint junior staff raise.
• Rotating priority. The order shifts each cycle, so whoever bid first this year bids last next year. Fairer over time, and it requires accurate records of past awards — which is where it usually breaks.
• Lottery. Randomised priority. Often used as a tie-breaker after seniority or rotation rather than as the primary rule.
• Ranked preference matching. Employees list several acceptable periods and the system works down the list, producing far better overall coverage than a single-choice bid.
• Hybrids. Seniority for the first round, rotation or lottery for contested remainders, is the most common real-world arrangement.

Where it’s used

Bidding is standard in airlines, healthcare, public safety, rail, manufacturing, and contact centres — any setting with fixed coverage requirements and a workforce that can’t all be absent at once. It’s near-universal in unionised environments, where the method itself is usually a bargained term.

Read more: How to Make Time Off Bidding Fair and Efficient

The legal constraints in the US

Collective agreements come first. Where a CBA sets the bidding method, deviating from it is a grievance, not a management decision. Check the agreement before designing anything.

Seniority systems get meaningful protection — but less than they used to. Two Supreme Court decisions bracket this:

In US Airways v. Barnett, the Court held that where a requested ADA accommodation conflicts with an established seniority system, that conflict is ordinarily sufficient to show the accommodation is unreasonable. The employee can still prevail by showing special circumstances — for instance that the employer frequently changes the system, or that it already contains exceptions, so employees have no settled expectation it will be followed.

For religious accommodation, Groff v. DeJoy raised the general bar: “undue hardship” now requires substantially increased costs, not the old more-than-de-minimis standard. It expressly preserved the principle that Title VII doesn’t require involuntarily stripping other employees of seniority rights — but it removed the easy fallback. An employer can no longer gesture at the bid system and stop: the question becomes whether the employee could bid elsewhere, whether a voluntary swap could cover it, and whether the cost of accommodating is genuinely substantial.

A bona fide seniority bid remains defensible — but each accommodation request still needs assessing on its own facts.

Frequently asked questions

Is time off bidding only for unionised workplaces? No, though it’s most common there. Any employer with hard coverage limits and over-subscribed peak periods can use it.

Does seniority have to be the deciding factor? Not unless a collective agreement says so. Rotation, lottery and hybrids are all legitimate, and rotation addresses the main fairness objection to pure seniority.

Can an employee be refused a period they bid for? Yes, if the coverage limit for that period is already met under the published rule. That’s the point of the system.