I would like to make my Roth contribution for 2022 as early in the year as possible. There are contribution limits based on Adjusted Gross Income. None of the sources I've read made it clear if it's the AGI for the contribution year, or from the year before.

To be clear, if I'm contributing in 2022, is it the AGI from 2021 or 2022 that matters for my contribution limits?

I assume it is 2022, but if that's the case, how can I make my contribution early if I can't predict my AGI for 2022 in Jan 2022? My income is somewhat hard to predict.