"a valued client" is correct and usable in written English.
You can use it when referring to a person or organization that has a good working relationship with your company or service. For example, "We thank our valued client for their continued loyalty and support."
Jonathan was a valued client, a dear friend, and a man of enormous talents and achievements.
The New York Times has a quarter-page ad from JPMorgan Chase that reads "More than a valued client.
The partners and employees of Cooley Godward Kronish mourn the loss of Charlotte Barth, a valued client and friend.
And one of Mr. Nobil's partners called the California firm to explain that Mr. Chesnick was a valued client.
If nothing else, the SAT is a big business, and Mr. Caperton does not want to lose a valued client.
Benny Greenspan loses a valued client when the man gets treated by a psychiatrist who tells him to retire from the movies.
Bernstein Real Estate BERNSTEIN -- Sidney J. Hubert J. Brandt, Richard A. Steinberg and Willa I. Lewis and the attorneys and staff of Brandt, Steinberg & Lewis note with great sadness the passing of Sidney J. Bernstein, a long and valued client, a true gentleman and a good friend.
Bill was a long-standing and valued client who will always be remembered for his high moral character and genius for innovation in real estate finance.
Consequently speakeasy owners who last night said farewell to old and valued clients over a last drink were in happier mood to-day when they learned that Utah had given them another day's grace.
Executives will often go online, and pick up a few items for their most valued clients while also buying for loved ones, he said.
Besides his Topman capsule, Price designs a small amount of womenswear for valued clients, among whom is the Duchess of Cornwall.
