Ive had the 5695 pop up on 3 different clients now, insisting I mark PartII Line 17a.  One of them had an amount in the lifetime limitation smart worksheet from 2017, so I didn't think much of it, they had nothing this year, so I checked a box. 

The next one didnt have anything in the lifetime limitation smart worksheet, ok, the season is early, may be a program quirk...they had nothing this year, so I checked the no box and moved on....(now Im banging my head trying to remember which client it was so I can investigate more)

The third one, showed nothing in the lifetime limitation box either, but I had some free time and I dug back through their prior year returns and found they had the $500 credit in 2016, but couldnt use it (no taxable income), so I think the open checkbox is coming from somewhere, even though the 2019 form 5695 shows nothing about this prior year, its not just random.

Does anyone know offhand (I havent even tried to research it, Im being lazy, its still dark on a Sunday morning and this just popped in my head), should this credit that my client had back in 2016 but couldnt use, is it supposed to carryover (which I dont see happening anywhere) or is it a use or or lose it credit, and if so, could they still use it again in the future since it wasnt ever really used before?   

(its actually a moot point with this particular client, they wont need to file returns anymore, they dont have enough income (retired on SS with a small pension), but Id like to keep it in my mental rolodex for future clients)