The phrase "a letter certifying" is correct and usable in written English.
You can use it when referring to a document that confirms or verifies certain information or qualifications.
Example: "Please provide a letter certifying your employment status for the loan application."
Alternatives: "a document verifying" or "a note confirming".
…a student gives me a letter certifying a need for an accommodation?
Instead, Mr. Choy will write a letter certifying that the student is in good standing and endorsing the internship on behalf of the university.
Our international-student office asked me to sign a letter certifying that this job is an "integral part of her academic program".
Mr. Gonzalez told employees they had until 5 p.m. on Tuesday to turn over to his office any documents relevant to the investigation, and they must sign a letter certifying that they had complied.
The week after a relative paid his bail, the Banc of America Investment Services in Miami provided Mr. Diveroli a letter certifying that his company had cash on hand to begin buying munitions on a large scale.
The family existed in a system in which state adoption law allowed the couple to receive $30,000 in annual stipends for doing little more than writing a letter certifying that their adopted children were still in their home.
Deciding that I was a suitable candidate for a medicalmarijuana recommendation, Dr. Dean took my money and provided me with a quick tutorial on strains of pot — indica offered a "body high," whereas sativa was "more heady and abstract" — along with a signed letter certifying that I was a patient under his care.
However, once you have been punched in the stomach, you can simply give your Stomach Puncher your address and Social Security number, pay a modest convenience fee, and, in three to four weeks, you will receive a notarized letter certifying that you have already been punched in the stomach.
In September, Pima suspended Mr. Loughner and told him not to return without a psychologist's letter certifying that he posed no danger.
According to pharmacy records and customer invoices, in July, 2000, for example, the month that Malakoff wrote the letter certifying Cheney's good health, he purchased thirty bottles of a synthetic narcotic nasal spray called Stadol from two mail-order drug-supply companies.
Late Thursday, the State Emergency Management Office sent the Federal Emergency Management Agency its annual letter certifying the emergency plans of the four counties around Indian Point -- a certification that critics have fought vigorously in recent days.
