USAGE NOTE FOR REASON Source: Dictionary.com The construction reason is because is criticized in a number of usage guides: - The reason for the long delays was because the costs greatly exceeded the original estimates. One objection to this construction is based on its redundancy: the word because (literally, by cause ) contains within it the meaning of reason; thus saying the reason is because is like saying “The cause is by cause,” which would never be said. A second objection is based on the claim that because can introduce only adverbial clauses and that reason is requires completion by a noun clause. Critics would substitute that for because in the offending construction: The reason for the long delays in completing the project was that the costs. … Although the objections described here are frequently raised, reason is because is still common in almost all levels of speech and occurs often in edited writing as well. A similar charge of redundancy is made against the reason why, which is also a well-established idiom: The reason why the bill failed to pass was the defection of three key senators. Reason is because versus Reason is that Source: Google Ngram Viewer The link below shows that the phrase "reason is that" is used 18 times more often than "reason is because". https://books.google.com/ngrams/graph?content=reason+is+because%2Creason+is+that&year_start=1800&year_end=2019&corpus=26&smoothing=3 The expression “The reason is because…” is redundant. “The reason I did not buy a new computer is because I did not have enough money .” Use “that” instead of “because” “The reason that I did not buy a new computer is that I did not have enough money .” The expression “The reason why…” is redundant. The word reason means why, so “why” is redundant. Use that instead of why Incorrect: The reason why I could not take/sit the exam is that I was very sick. Correct: The reason that I could not take/sit the exam is that I was very sick.

They have the exact same meaning and both can be used. I found this quote online: ‘The reason is because is a standard English phrase, one coming from the pen of good writers (Bacon, Frost, Wodehouse) for 400 years. It’s grammatically fine, and its supposed redundancy is at worst mild. You’re welcome to use the reason is that instead, as both are standard, but there’s no good reason to oppose the reason is because.’