Some of the oldest cases that discuss the changes in a contract, where those changes were not communicated with the surety, hold that those changes made between the principal and creditor necessarily discharge any duties by the surety. This is regardless of whether those changes are harmful or helpful to the surety.
Thus, a surety that entered into an agreement for a performance bond regarding the duties of another would be discharged from any and all liability for any default after that change as long as the surety did not assent to those changes. This is a substantial benefit to the surety as they can be released from liability, and sometimes substantial liability, even when the contractual changes would benefit them. These guarantors would then look for any changes to the contract, including work orders, etc., so that they could escape liability.
For example, let’s assume that a surety has guaranteed the work of a contractor for a road construction performance bond. Then the local municipality decides that, after work has started on the job, to increase the amount of collateral that the contractor has to allocate for the job. This change, by itself, would (under the old rules of interpretation of surety contracts) invalidate the surety company’s obligations. This is despite the fact that the surety company is better off, as the contractor has had to engage more of their personal collateral on the contract.
Of course, the equity of the situation also swings the other way. In many cases (most cases?), the surety company was damaged by the change to the contract as the principal would have increased risk or authority (in case of a personal fidelity bond). But the real reason underlying this rationale was to put the burden of communication on the parties that had access to the information: the principal and owner. That is because the surety company has no way to know whether the contract itself was changed or amended in any way unless those changes were disclosed to it by the parties to the contract. Given this lack of information flow between the parties, it was decided that the best option was to require those with access to also have the burden of disclosing those changes.
The newer case law did away with the very strict interpretations above. The later cases held that a surety would not be summarily discharged by any changes in the contract. Instead, only changes that materially affected the performance of duties under that agreement, and that were not assented to by the guarantor, would cancel the contract. Those changes that did not increase the risk of the surety would not then go ahead and ruin the effectiveness of that contract.
For example, let’s assume that a surety company would guarantee the performance of duties by a bank manager who had access to the entire bank, including the vault. Then, that bank manager was promoted to vice president. This increase in title and duties would, under the old laws, eliminate any indemnification on behalf of the surety. However, under the new interpretation of the agreement, it would not. The surety company would have the same risk. That is, the person would have the same access to any funds as they did before and would not, in and of itself, have any additional access that would increase the risk of the guarantor. Instead, the increase in duties would be in relation to the job, but those changes would not affect the guarantor’s risk profile.
Surety Bond Companies have had a wild ride when it comes to changes in contracts. Under the original interpretations of those agreements, any change that was not assented to by the surety would void the contract. The rationale was that the principal and owner had the information and needed to convey that information to the surety. However, this interpretation changed over time so that the contracts would only be voided if the changes were harmful to the guarantor company.