What is a nexus letter and when do I actually need one?

A nexus letter is a written medical opinion from a qualified provider stating that your current condition is "at least as likely as not" (≥50% probability) related to your military service, either directly or secondary to another service-connected condition. You need one when: - Your STRs don't clearly document the in-service event. - You're filing a secondary condition claim. - You're appealing a denial where "no nexus" was the reason. - The condition isn't presumptive and the connection isn't obvious. You probably don't need one when: - The condition was diagnosed and treated in service (STRs do the work). - It's a presumptive condition under PACT Act, Agent Orange, Gulf War, or Camp Lejeune. - A VA examiner is expected to provide the opinion at your C&P exam. Cost of a private nexus letter typically runs $500–$2,500 depending on the specialist and complexity.