Such a “requirement” is illegal. https://www.nlrb.gov/about-nlrb/rights-we-protect/your-right...

But in the US, federal labor law makes it illegal for employers to prevent employees from sharing pay information (at least for employees who are entitled to unionize).

They can request it, but can't stop you if you do.

You can also request them to do likewise, with similar recourse.

A request is nothing without teeth behind it.

I never have but I have never been told I couldn't share pay information. Certainly I have with my accountant and financial advisor. I've also been asked when applying for a new job whether or not I've been 100% forthcoming.