This means each party must give something of value in order for there to be a valid contract. This can be a positive act such as doing some work or giving something to the other party such as money or property. There are two main types of valid consideration:
The consideration must have some value but it does not have to be equal value, so it must be sufficient but it does not need to be adequate.
Chappell v Nestle (1960)
In Chappell v Nestle (1960) the court stated the consideration must have some economic value but it can be small, in this case, chocolate bar wrappers were said to have enough economic value to be deemed adequate consideration.
Past consideration is not valid; this is something that has already been done at the time of the agreement.
Re McArdle (1951)
A couple lived with the husband’s mother. The wife made improvements to the house. When the mother died, she left the house to her son and other children. The other children promised to compensate the wife for the money she spent doing the improvements.
The court held that a promise to pay for work done that had already been done voluntarily was not a consideration; it was past consideration and therefore did not form the basis of a valid contract.
However, this rule is different if X requests something from B before the contract comes into existence but there is a mutual understanding that the contract will exist and there will be a payment.
Lampleigh v Braithwaite (1615)
Braithwaite (defendant) killed someone and then asked Lampleigh to get him a pardon from the king. Lampleigh managed to get the pardon and Braithwaite promised to pay him £100. Braithwaite did not pay him. The courts held that this was consideration as it was directly linked to the earlier request and both parties understood that payment would be made.
(Keep in mind that this is a very old case so it does not mean that you can contract killers all that matters in the consideration principle).