The phrase "a letter concerning" is correct and usable in written English.
You can use it when referring to a letter that addresses a specific topic or issue.
Example: "I received a letter concerning the upcoming changes in the company policy."
Alternatives: "a letter about" or "a letter regarding".
The Durst Organization got a letter concerning the Helena, a 600-unit apartment building at 57th Street and 12th Avenue.
After reading the article on Dr. David Bank, I felt compelled to sit down and write a letter concerning this excellent doctor.
A letter concerning a territorial dispute from Japan's leader, Yoshihiko Noda, was rejected by South Korea, which then sought to return the correspondence and was itself refused.
A Mrs. Clement K. Stodder, of 21 Peniman Road, Brookline, Massachusetts, recently mailed a letter concerning certain irrelevant matters having to do with her alma….
When John Szarkowski, the director of the department of photography at the Museum of Modern Art at the time, wrote a letter concerning the purchase of five of Mr. Link's prints in the mid-70's, he wrote, "Among other things, Link is a demonstration of the fact that, for an artist, there is no substitute for a fixation".
A Letter concerning Toleration.
Earlier this week, a mother of a young Tennessee Titans fan harshly condemned Carolina Panther Cam Newton in an open letter concerning a certain touchdown dance by the quarterback.
After the final visit to the outpatient clinic a brief letter concerning the study start and completion will be sent to the patient's General Practitioner.
Weeks before the release of Independiente, Arjona published an open letter concerning his past relationships with recording companies.
In an open letter concerning slave-owning ancestors, author Thomas Norman DeWolf tells actor Ben Affleck that "The harm our ancestors caused is not our fault.
The reporting form and an explanatory letter concerning the duty to report were sent to the clinician attended by the patient.
