A bar bill or bar tab is an account of debt owed to a bar by a patron for goods and services.

While playing Dixon Hill on the holodeck, Jean-Luc Picard once forgot to bring money with him to pay his character's bar bill. The bartender Rex gave him another drink nevertheless. (TNG: "Manhunt")

While under the impression that Julian Bashir and Miles O'Brien were dead, Quark gave a toast in their honor, "They were good customers. They always paid their bar bills on time." Quark could think of no greater tribute. (DS9: "Armageddon Game")

In 2371, Tom Paris told Captain Kathryn Janeway that Chakotay considered him a mercenary, willing to fight for anyone who paid his bar bills. (VOY: "Caretaker")

While under the influence of the Bajoran Prophets in 2371, Grand Nagus Zek bought everyone present in Quark's Bar a drink and asked Quark to put it on his tab. (DS9: "Prophet Motive")

After being informed of Morn's apparent destitution at the time of his death, Quark commented that Morn had always paid his bar bills on time and that money had to have come from somewhere. (DS9: "Who Mourns for Morn?")

Worf disputed responsibility for a bar bill with Quark, but eventually paid it after Quark mentioned that it would not be good if word got out that he was refusing to honor the debts incurred by his own House. (DS9: "Prodigal Daughter")