How long is a bridge letter valid?

A bridge letter has no printed expiration because it isn’t a certificate — it’s a dated statement that controls have held since the last report’s period ended. Reviewers therefore watch two numbers: the size of the gap the letter spans, and how recently it was signed. A letter from January loses persuasive power by May even if nothing changed, because five months of “nothing changed” is itself a claim that needs refreshing.

The working conventions are stable across procurement teams. A gap of roughly three months raises no eyebrows; approaching half a year, expect follow-up questions; beyond that, the letter stops carrying the conversation and the buyer starts asking why the next report is so far away. Hence the standard cadence — reissue quarterly, and on demand for any deal in flight, each one newly dated rather than recycled.

A gap that keeps growing is an audit-calendar problem wearing a paperwork costume: keep observation periods contiguous and the stretch a letter must cover collapses to the auditor’s writing time. The letter’s full anatomy and an adaptable example live on the SOC 2 bridge letter page; the compact definition is at bridge letter.