My husband and I got married, halachikally, in January. We are not yet legally married. I would like to have him sign a halachic postnup. Here are my questions:

A. Do we need to have a financial prenup in place in order to have a halachik prenup? Or can it stand alone in civil court? Or it it simply an addition to the ketuba and only holds up in Bet Din?

B. If we sign the halachik postnup, does it only hold up in the city you signed it in? Ex, if we signed it in Miami but later decide to move to NY, does it still apply?

First of all, mazal tov!

Thank you for reaching out to us with your questions,  I'll try to answer in order.

A) The halakhic postnup is not dependent on a separate financial prenup.  It is intended to be a civilly enforceable contract, with an arbitration clause that requires you to go to beit din first. Civilly, the beit din functions like any other arbitration panel, religious or secular, and so long as its decision is not arbitrary, capricious, or unreasonable, it should be upheld and enforced by the civil courts.

B) The halakhic postnup is intended to be enforceable wherever you move.  Since different jurisdictions have different laws, and those laws change, and the document has not been tested in court in many jurisdictions (happily; this means that it works without anyone having to sue), no one can guarantee that it will be upheld everywhere. But that is the intent.

Mazal tov again.  I think it is a service for the community for you and your husband to sign this document.  Please feel free to ask followup or clarification questions.