A guaranty makes a third party answerable for the borrower’s obligation. Disputes almost never concern whether the guarantor signed; they concern whether something later discharged them.

Modification of the underlying obligation. At common law, a material change to the principal obligation made without the guarantor’s consent can discharge them. Which is why nearly every commercial guaranty contains sweeping consents in advance — to extensions, modifications, releases of collateral and of co-obligors — and why those clauses are the first thing to read.

Impairment of collateral. A creditor that releases or negligently loses collateral may reduce the guarantor’s exposure by the value lost, unless waived.

Absolute or conditional. An absolute guaranty of payment allows the creditor to pursue the guarantor immediately on default. A guaranty of collection requires the creditor to exhaust remedies against the borrower first. The distinction is determined by the wording and it decides the sequence of the whole enforcement.

Continuing or transaction-specific. A continuing guaranty covers future advances until revoked in the manner the document specifies; revocation provisions are strict and often ignored.

Spousal and joint issues. Where only one spouse signs, the reachable assets may be far narrower than the lender assumed depending on how property is held.