Doing K-1 after trust distributions

I am getting close to doing our family's trust 1041 using TT, but figuring out the K-1 will be the hard part.
If we begin a monthly distribution during 2021, then can we make the decisions/determinations about whether the money was principal or interest or capital gains or whatever in early 2022 as we do the 1041 and K-1s for 2022.  Is that a reasonable plan, or must we make all the determination before distribution, even though they won't be reported till the next tax season?
thanks