Restitutionary claims must respect contractual regimes and the allocations of risk made under those regimes. In Pavey & Matthews Pty Ltd v Paul, in a passage cited with approval by French CJ, Crennan and Kiefel JJ in Equuscorp Pty Ltd v Haxton, Deane J said:
'The quasi-contractual obligation to pay fair and just compensation for a benefit which has been accepted will only arise in a case where there is no applicable genuine agreement or where such an agreement is frustrated, avoided or unenforceable. In such a case, it is the very fact that there is no genuine agreement or that the genuine agreement is frustrated, avoided or unenforceable that provides the occasion for (and part of the circumstances giving rise to) the imposition by the law of the obligation to make restitution.'
In Pan Ocean Shipping Co Ltd v Creditcorp Ltd ('The Trident Beauty'), Lord Goff of Chieveley spoke to similar effect:
'[A]s a general rule, the law of restitution has no part to play in the matter; the existence of the agreed regime renders the imposition by the law of a remedy in restitution both unnecessary and inappropriate'.
In Lumbers v W Cook Builders Pty Ltd (In liq), Gleeson CJ noted that the contractual arrangements in that case 'effected a certain allocation of risk' and that there was 'no occasion to disturb or interfere with that allocation' and 'every reason to respect it'. Gummow, Hayne, Crennan and Kiefel JJ spoke of taking 'proper account' of the contractual rights and obligations that existed, and said:
'[A]s is well apparent from this Court's decision in Steele v Tardiani, an essential step in considering a claim in quantum meruit (or money paid) is to ask whether and how that claim fits with any particular contract the parties have made'.
Their Honours noted that it is essential to consider how the claim fits with contracts the parties have made because, as Lord Goff 'rightly warned' in The Trident Beauty, 'serious difficulties arise if the law seeks to expand the law of restitution to redistribute risks for which provision has been made under an applicable contract'.
In MacDonald Dickens & Macklin (a firm) v Costello in the Court of Appeal of England and Wales, Etherton LJ, with whom Pill and Patten LJJ agreed, in rejecting a restitutionary claim, said:
'The general rule should be to uphold contractual arrangements by which parties have defined and allocated and, to that extent, restricted their mutual obligations, and, in so doing, have similarly allocated and circumscribed the consequences of non-performance. That general rule reflects a sound legal policy which acknowledges the parties' autonomy to configure the legal relations between them and provides certainty, and so limits disputes and litigation'.
Accrued contractual rights
In circumstances where the respondent has enforceable contractual rights to money that has become due under the contract, there is no room for a right in the respondent to elect to claim a reasonable remuneration unconstrained by the contract between the parties. As Deane J explained in Pavey & Matthews, in such a case there is a 'valid and enforceable agreement governing the [respondent's] right to compensation', and there is therefore 'neither occasion nor legal justification for the law to superimpose or impute an obligation or promise to pay a reasonable remuneration'. To allow a restitutionary claim in these circumstances would be to subvert the contractual allocation of risk. As Beatson has said:
'[W]here P confers a benefit on D pursuant to a contract, the valuation of that work is a matter of contract, which ... respects the parties' valuation. Valuation is in a sense part of risk allocation: P is taking the risk of market rises and D of falls in the market. To allow P to recover anything other than the contract value - such as the objective value, the market value, or a reasonable value - would be to reallocate that risk.'[14]