If taxes were a matter of plunking numbers in and getting forms out, any idiot could do them and then no one would pay us the big bucks.

So Box 20 is for informational items, where you have to know enough about taxes to choose your own adventure.

Bonus depreciation adjustment for non-conforming states is pretty self-explanatory, and the K-1 kind of explains it, too, in the ant-type pages in the back. If your client is a resident of a state that didn't conform to bonus depreciation, that's the state depreciation adjustment. The "state if different" column might work, but you might have to play around some. If your client's state conforms, you can disregard this. If you don't know whether a given state conforms or not, its forms instructions will sometimes say, or you can Google "bonus depreciation state conformity" and hope for the best.

H2 and H3 relate to UBTI (learn more by googling it), which only applies to things that file a 990-T: tax-exempt entities including retirement plans and IRAs. Your client is a person? Not relevant to you.

Basis (my recollection is that this is original cost basis, not current tax basis; if the capital account is positive, it usually but not always approximates tax basis for most PTPs) and accumulated passive losses are the entity's best guess as to those things. If the client comes to you with a PTP they've owned for prior years and none of the back K-1s and none of the old tax returns, it's better than nothing but not a lot better. Woe betide you if this client owned the PTP in prior years and doesn't have every K-1 and every tax return and every worksheet. So much woe. Heck, woe betide you if they do have them all and they're all prepared correctly. Woe is the nature of PTPs.