[Svartalfiar]

The 22% is just an optional withholding rate for the employer. Bonuses are taxed as ordinary income to the employee, just like salary.

Yes my bad, I meant the employer withholds at that rate, not that your year-end taxes tax it at that rate specifically.

Now what I'm not sure of, is between the percentage and aggregate methods, is the 22% a minimum withholding? Or using the aggregate method can they withhold at your top rate if it's lower than 22%?

[semimojo]

Or using the aggregate method can they withhold at your top rate if it's lower than 22%?

Looking at the IRS guidance I think it's strictly the employer's choice, provided the supplemental income is less than $1M. You have to withhold 37% of supplemental income over $1M.