My sister is having a 50th birthday party and charging everyone $90 to chip in for the open bar. Is that fair?

Imagine Sharon, 47, whose sister Denise is turning 50 and throwing herself a birthday bash in her condo’s party room. Denise’s digital invite asks every guest to pay $90 toward the open bar.

Sharon is shocked, knowing $90 is steep for a number of their friends, several of whom don’t even drink. She tells Denise that’s not an “open bar” — it’s a “cash-upfront” bar.

Denise retorts that she’s already spending a ton on catering, including hiring a bartender and server for the night. Sharon still doesn’t think it’s fair, especially as the condo party room is a free venue.

Here’s what etiquette experts say and how to handle such requests as a host and as a guest.

Etiquette around asking birthday guests to pay for booze

Etiquette experts agree: It’s rude to ask guests to pay for anything at your birthday party, including alcohol.

Miss Manners (a.k.a. Judith Miller) said as much to a reader invited to two birthday parties — a friend’s 30th and another’s 40th — in one day and expected to pay for both.

“The self-celebration, complete with self-selected material tributes but guest sponsorship, is, as you say, rampant,” Miller wrote. “The only way this crude practice will stop is if the targets refuse to cooperate.”

That was all the way back in 2007. The practice has only revved up since then. In 2018, Washington Post personal finance columnist Michelle Singletary, launched her self-styled #GuestsDontPay campaign to protest the practice.

“I now respectfully decline such invitations,” she wrote. “If it isn’t clear whether I’ll be charged, I ask. If I have to pay, I don’t go. I’ll offer congratulations and perhaps send a card or gift later. But I will not be a party to this etiquette breach.”

Singletary received backlash from millennials who said they had to ask friends to cover birthday food and drinks at fancy venues, prompting Singletary to write a follow-up saying millennials shouldn’t expect similarly cash-strapped friends to pay for meals and drinks out.

Elain Swann of The Swann School of Protocol told CNBC that hosts should never ask guests to cover the cost of anything — including drinks.

“You’re supposed to bring it together and do all the things, unless it’s potluck style,” she said.

Still, people like Denise continue to ask their guests to help pay the meal and bar tab at birthdays. What is the best way to handle this?

Negotiating pay-to-party invitations

Having guests pay $90 for the bar tab upfront may prevent lineups associated with bartenders negotiating cash guest by guest, but it may cause more consternation than it’s worth.