Imputed income taxation (domestic partner health benefits)

We were really excited to get company sponsored benefits this year, until I noticed an imputed income entry on my paycheck. Much googling commenced, and now I feel like it's going to bite me in the rear cometh the taxman for 2022. It's significant enough to potentially cause many thousands of tax owed, as I didn't see any change to federal withholding on my last check (next one coming in several days). Soc Sec and Medicare (and State) did go up, as did my taxable gross. I've sent them an email on this and eagerly anticipating their response.   Not sure why they wouldn't withhold the fed tax.

I just wanted to double-check, that imputed income counts towards the overall gross, and that all usual suspects (including federal) is owed on that. Any strategies to help offset it? Contribute more to 401k? lol

Thanks!