Uniform Commercial Code (UCC): Primary source of commercial contract law in the US, particularly relevant if the original agreement involves goods.

State Contract Laws: State-specific variations in contract law that must be considered as contract enforcement varies by jurisdiction.

Statute of Frauds: Legal requirement that certain types of contracts must be in writing to be enforceable.

State Statute of Limitations: Time limits within which legal action must be taken regarding contract disputes in the applicable state.

E-SIGN Act: Federal law ensuring the legal validity of electronic signatures and records in interstate commerce.

Uniform Electronic Transactions Act (UETA): State-level law governing electronic signatures and records in business transactions.

Industry-Specific Regulations: Sector-specific federal and state regulatory requirements that may affect contract extensions.

Good Faith and Fair Dealing: Legal principle requiring parties to deal honestly and fairly in contract formation and performance.

Consideration Requirements: Legal principle requiring exchange of value for contract modifications to be valid.

Corporate Authority Rules: Laws governing who has legal authority to execute contract extensions on behalf of a business entity.