Everything was executed and filed based on the like-kind exchange rules. The problem is I did not do their taxes for 2023 and I built that one first and started working on 2024 return.

To answer your question, the gain shows up on form 4797 and it's coming from form 8824. Again, probably it's because I did not do their taxes in 2023 and just tried to make that one before working on 2024 return.