When I googled for 1120-S K-1 instructions I got this pdf which doesn't mention LLC's:
https://www.irs.gov/pub/irs-pdf/i1120ssk.pdf
Your link is much better :-).
I read another article that said ownership interest in an LLC can be done in two way- units or percentage. This all still seems kind of a kludge to me because our LLC has no units. I don't know what personal tax software for preparing 1040's will do with boxes D, G and H. Before 2020 there was only the allocation percentage (now Box G) on the K-1.
What one needs for a non-dividend distribution (Box 16 code D) that now triggers requiring form 7203 is basis, and none of these K-1 boxes provide that. It must be kept track of by the member. However for our simple two-member LLC I think basis is the shareholder's percentage times the amount in the 1120-S page 5 Schedule M2 line 1, "Balance at the beginning of the tax year".
