Britney Spears tipped a waitress $100 after forgetting to pay her bill.

The 32-year-old singer felt ''horrible'' after she and her boyfriend, David Lucado, mistakenly walked out of The Cheesecake Factory in Thousands Oaks, California without settling their $30 bill after eating an appetiser and a salad there this week.

A source told gossip website that the blonde beauty decided to give the waitress that served her a 300 percent tip on top of the bill after she was made aware of her blunder.

A source previously said the couple, who started dating in March 2013, told the waitress that her bodyguard would pay the bill and left with a doggie bag of leftovers.

But the security guard never paid, as he thought Britney, who has sons, Sean, eight, and Jayden, seven, with ex-husband Kevin Federline, had already done it.

Meanwhile, it was recently revealed that Britney and David are thinking about having a baby together when her Las Vegas residency ends next year.

The insider said: ''Britney cannot wait until the Vegas show is done because she wants to start a family with David. She says she will get pregnant as soon as the show is finished!

''David is always with her in Vegas and they act like an old married couple together. He is really good with her kids and has taken to the father role pretty easily.''