Is it okay to use AI to write a cover letter?

Yes, with conditions, and the conditions are the whole answer. Using a tool to help you write is no more dishonest than using a spellchecker or asking a friend to read a draft. Submitting something you have not read, that contains claims you cannot back up, is a different act entirely, and that is what employers object to.

The line is not the tool. The line is whether the letter is true and whether you would stand behind every sentence in an interview.

What is genuinely fine

  • Getting unstuck when you are staring at an empty page.
  • Tightening something you wrote that runs long.
  • Fixing grammar, and particularly if English is not your first language.
  • Rewording the same real experience for a different role, which is most of what tailoring actually is.
  • Checking you have answered what the ad asked.

What is not

  • Anything invented. A skill you do not have, a number you did not achieve, a responsibility that was somebody else's. This is the one that ends offers, not just applications.
  • Sending it unread. If you have not read it, you cannot defend it, and you will be asked about it.
  • The same letter with the company name swapped. Employers reject these at a striking rate: 62% of employers in a United States survey said they reject AI written applications that show no personalisation.
  • Anything you would be embarrassed to be asked about. A useful test, and a fast one.

What employers are actually reacting to

Almost no employer has a policy against AI assistance, and very few would know either way. What they react to is an application that took no thought, because it tells them what working with you might be like. The objection is to the absence of effort, not to the presence of software. That distinction is worth holding onto, because it tells you exactly where to spend your own time: on the specifics only you know, and not on the sentence construction.

A test that works

Read the letter back and ask two questions.

  1. Could this have been sent to a different employer without changing anything? If yes, it is not finished.
  2. Is every fact in it something I could talk about for two minutes? If not, take that sentence out.

A letter that passes both is fine, no matter what helped you write it. See also whether employers can tell, which is a different question with a more uncomfortable answer.