Signing surety can destroy the advantages of ANC marriages and trusts
We take a lot of trouble to ensure that we get married under ANC so that there are two separate estates and if one is bankrupt the other isn’t. Likewise we set up discretionary trusts to protect assets from creditors if one of us should be bankrupt. Signing surety destroys these protections.
The trust’s company is unlikely to be able to raise a bond unless you sign surety, so that one is pretty much unavoidable. What should be avoided is both of you signing surety, because that means that the marriage under ANC is also no protection. It is the directors of the company that always have to sign. If your spouse is not a director, then the bank has no right to expect him or her to sign and you should refuse. Also make sure that it is always the same one of you that signs all such suretyships so that the other estate is safe. Then ensure that the other estate owns whatever assets are outside of the trust.