Definition of Variation Order Request (VOR)
The precise meaning will depend on the relevant contract, but a variation order request is sent by a contractor to their client when they think that they are required to do extra work that is not covered by the contract, or where they think that they are not able to complete the work under the terms of the contract. This might be because of new or unexpected requirements, or new information that affects the design or scope of work.
A VOR must be issued ‘without undue delay’, or the contractor loses the right to claim that the work is a variation - see DVO