Stand surety, act as surety

A company 'B' owes money to someone and a different company is responsible for paying the debt. If the debt isn't paid by the 'B' company, the other company has to pay off the debt themselves or they have to appear in court instead of the 'B' company.

Could 'stand surety' or 'act as surety' be used in this example or is there a different word that would convey the same meaning? I think that these terms might be too formal but I'm not sure.

Thank you.