TCJA took away the deduction for union dues back in 2018.  Some states still allow them, so they get entered in the same place as usual (misc itemized deductions, unreimbursed employee business expenses, Sch A)....you just wont see any deduction for them on the federal return.

They should go in the same place you entered them last year.

"My" union dues would go into a Turbo Tax return, here:

https://ttlc.intuit.com/community/discussions/discussion/03/302

Your Client's union dues would be a different issue.

when i read posts like the OP made... i just think I should probably double my fees.  Why don't they let people buy a software package and then perform brain surgery?   smh

TurboTax and QB people get lost on the internet. That's the typical issue.

Union dues go on schedule A under "State only" lines.