Hi Beverley.

In my experience from speaking to family law practitioners over the years, the most common challenges are:
1. Signing a BFA too close to the date of a wedding or date moving in together. The typical claim is that the effected person may have been pressured into signing the BFA. For example, the stronger financial party may hint that the wedding is not going ahead unless the BFA is signed. The certifying lawyers now will not sign a certificate if they believe there is a possibility of this happening. They will typically advise to sign the BFA after the date of the wedding or after the date of moving in together.
2. Children of the relationship. If parties sign a BFA and they subsequently have a child or children, and the enforceability of the BFA may be unfair on the welfare of the children or unfair on the custodial parent of the children, then the Court may vary the terms of the BFA to make it more equitable. I have no personal experience of this type of claim, so I am unsure as to what specific arguments are made.
3. Future needs. If the fundamental circumstances of a party changes during the relationship (say due to a chronic serious health condition) then the terms of the BFA can be varied by the Court to allow for the future needs of the effected party.
4. One party claiming they did not understand the implication of the BFA. This is harder to argue as the role of the advising lawyers is to be SURE that the party they are advising understands the implications.
I have no statistics to share about the success or otherwise of challenges. If anyone does have further info, please let the forum know.

Kind regards,