invitation wording

Now I want to write attire on it but I'm not sure to write semi formal required/preferred or formal attire preffered/required

Now my FH and the GM are wearing suits not tuxes but I don't want ppl showing up in polo shirts and khakis or jeans! So I'm not sure which one to write on there!?! Anything will help! TIA

definitely don't write 'formal' because that could imply black tie.

I would say 'cocktail attire'

This explains all the different ones
guest attire