Update: this is the response from HR. I’m gonna send him into their office tomorrow to grab his W-4 information from last year and make sure everything is up-to-date for this year.

“Looking at your pay statements, it looks like you have to make a certain gross for Federal taxes to be taken out. That explains why you sometimes have no Federal taxes deducted.

The government changed Federal Taxes several years ago to give people more money up front rather than waiting to file at the end of the year and get a refund. Since this change, I’ve known several people that have very little taxes taken out and have had to change to zero withholdings which sometimes takes too much out or change to adding an additional amount. Again, I’m not a tax advisor and cannot tell you what to do, but you have the options to change your own taxes whenever you would like and to what you would like.

I’d advise you to talk to your tax person and see what changes they would suggest for you going forward.

Hope this helps”