If you do not make an agreement on financial matters legally binding, then your financial claims against one another remain open and your partner could make a claim against you in future. For example, in the future, if you receive a large inheritance or your pay should increase, your partner could return to make a claim against you.
To make an agreement legally binding, it must be drafted into a document called a consent order, which must be submitted to the court for approval. This will need to be submitted with disclosure, the form of this disclosure will depend on whether you are already in legal proceedings or not. It is very important to engage a lawyer to draft the consent order as they will be able to ensure that all relevant claims are dismissed fully and properly, minimising the need for (and cost of) future court proceedings.