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This principle allows a court to incorporate a past benefit (see: Consideration) into a new Contract, and thereby deem that the contract has sufficient consideration to be enforceable. In general, past benefits are not consideration (see: Re McArdle (1951)). Assumpsit can only be invoked in the following circumstances:

• the past benefit must have been at the explicit request of the person against whom the claim is made, and
• there must have been an assumption that the benefit will be recompensed in the future, and
• all the other requirements for a valid contract must be in place. Assumpsit can not be applied if the contract would not have been a good one even if the consideration had been valid.

For example, if A asks B to do some work, and A does, knowing that some recompense will be offered, then B offers a payment, this sequence of events constitutes a contract and is enforceable. On the other hand, if B does the work and then brings it to the attention of A, who offers payment, this is not enforceable. The latter situation is a straightforward case of past consideration. Implicit assumpsit would, therefore, not have helped the claimants in Re mc ardle because they did the work for which they were claiming at their own behest, not on the request of the defendant.