What to do when things go wrong

• collateral contracts – is there a collateral contract for the performance of the variation?;
  

• restitution or quantum meruit – a contractor deprived of contractual entitlements might be able to claim compensation because the principal has been unjustly enriched by performance of the variation;
  

• the Competition and Consumer Act 2010 (Cth) (formerly, the Trade Practices Act 1974 (Cth)) – either party might claim to be entitled to remedies in reliance upon the conduct of the other party;
  

• waiver / estoppel / promissory estoppel – either party might allege reliance, to its detriment, on conduct of the other party.