Using commas correctly is crucial for clear writing, especially in the OET writing sub-test. Here are some basic rules to help you master comma usage  in OET Letter Writing:

Complex Sentences: These consist of an independent clause and a dependent clause. When the dependent clause comes first, it is followed by a comma.Example: After a full diagnosis is made, treatment will begin.Compound Sentences: These are made up of two independent clauses joined by a comma and a coordinating conjunction (for, and, nor, but, or, yet, so), or by a semi-colon and a conjunctive adverb followed by a comma.Example: The cause of her headaches was unknown, so Mrs. Trafford was sent to the specialist.Example: The cause of her headaches was unknown; therefore, Mrs. Trafford was sent to the specialist.Introductory and Transitional Phrases: These phrases, which come before the subject of a sentence, are followed by a comma.Example: On October 14th, Mrs. Parker underwent surgery for a broken ankle.Lists of Ideas or Items: Each item in a list is separated by a comma, including the final item before "and" or "or," known as the Oxford comma.Example: The patient was advised to take painkillers, antibiotics, and get plenty of bed rest.

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