Just like any other kind of legal contract a post nuptial agreement must be drawn up properly and following UK contract law. This is why it’s so important for both parties to get independent advice from their solicitors before entering into such an agreement. A specialist solicitor should draft your post nuptial agreement to give it the best chance possible of being adopted by the courts and make sure your provisions do not fall into any of the pitfalls which could cause them to conflict with existing law, such as ensuring the post nuptial agreement has future flexibility.
It is important that your post nuptial agreement is reviewed regularly to make sure it is still meeting both parties’ needs and is still fair. For example, it would be important to review it if you have a child.
As long as the agreement is still fair when the courts enforce it, both you and your partner have obtained independent legal advice and you have both fully disclosed your finances then it should be upheld by a court.