Can a financial agreement be set aside?

Yes, but only in limited circumstances.
A financial agreement (as defined by s 4 of the Family Law Act 1975, and commonly referred to as a binding financial agreement (BFA)), whether made before (s 90B), during (s 90C) or after marriage (s 90D), may be set aside or terminated by a court if, and only if, the court is satisfied that (s 90K):

  1. the agreement was obtained by fraud, including non-disclosure of a material matter;
  2. a party to the agreement entered into it to defeat or defraud creditors or with reckless disregard of creditors;
  3. a party to the agreement entered into the agreement to defraud or defeat the interests of, or with reckless disregard of the interests of, the other party’s de facto or spouse;
  4. the agreement is void, voidable or unenforceable;
  5. circumstances have arisen since entering the agreement that make the agreement or part of the agreement impracticable to be carried out;
  6. since entering the agreement, a material change of circumstances has occurred which effect the care, welfare and development of a child to the marriage and a party with the care of the child will suffer financial hardship if the court does not set the agreement aside;
  7. in making the agreement, a party engaged in conduct that was, in all the circumstances, unconscionable;
  8. a payment flag is operating under Part VIIIB on a superannuation interest covered by the agreement and there is no reasonable likelihood that the operation of the flag will be terminated by a flag lifting agreement under that Part; or
  9. the agreement covers at least one superannuation interest that is an unsplittable interest for the purposes of Part VIIIB.

The above ought to be kept in mind when entering into a BFA to limit the possibility of a BFA subsequently being set aside or terminated on an application to the court by the other party.
Alternatively, if you are seeking to set aside a BFA, seek legal advice (ie contact us) on the prospects of an application to the court.