So I just emailed my accountant since I was definitely interested (and I’m into taking every legitimate tax break I can).
He says this used to be ok but due to widespread abuse the IRS has specifically written rules about cruises severely limiting deductions. He says it has to generally be a North American ship in certain North American ports, and generally is limited to 2k or a (small) per diem based on govt employee standards, except for the actual conference registration fee. He also said unless the activity was actually on board, he’d be careful since there are “necessary” clauses in the guidance and if you can do the material from your home office, it may be illegitimate when it comes to an audit.
I trust this guy since he’s been doing my accounting for 15 years, and specializes in doctors. Definitely tries to maximize all my legal shelters over the years.
I’m sticking to my Hawaii or European in-person resort deductions. They can’t argue it wasn’t necessary if the conference was actually at XYZ resort with live speakers.