Commercial agreements & supporting documents · Working
Side letter
Also called: investor side letter, side agreement
ELI5
A separate agreement supplementing or modifying terms between selected parties.
Used in conversation
“Can we state who receives the right created by side letter, and when it applies?”
Pitch context
You will see “Side letter” in board papers, contracts, policies, risk registers and compliance reports when the discussion reaches commercial agreements & supporting documents.
Why it matters: In commercial agreements & supporting documents, a loose definition can change rights, obligations, approval, disclosure or enforceability.
Caution
Meaning, enforceability and required process vary by jurisdiction and agreement; this definition is not legal advice.
Sources & evidence · 11
Direct term-level sources and supporting source families.
- Y Combinator — The Handshake Deal ProtocolDirect source · practitioner · checked 2026-08-16
- National Venture Capital Association — Model Legal DocumentsDirect source · institutional · checked 2026-08-16
- U.S. Securities and Exchange Commission — Small Business Capital Formation GlossaryDirect source · primary · checked 2026-08-16
- U.S. Acquisition.gov — Federal Acquisition Regulation Part 15 — Contracting by NegotiationDirect source · primary · checked 2026-08-16
- UK Government — Groceries Supply Code of PracticeDirect source · primary · checked 2026-08-16
- U.S. Securities and Exchange Commission — Exempt OfferingsSupporting source family · primary · checked 2026-08-16
- Y Combinator — Safe financing documentsSupporting source family · practitioner · checked 2026-08-16
- Y Combinator — Series A Term Sheet TemplateSupporting source family · practitioner · checked 2026-08-16
- OECD — G20/OECD Principles of Corporate Governance 2023Supporting source family · institutional · checked 2026-08-16
- U.S. Securities and Exchange Commission — EDGAR and filing resourcesSupporting source family · primary · checked 2026-08-16
- National Institute of Standards and Technology — Computer Security Resource Center GlossarySupporting source family · primary · checked 2026-08-16