Everyone knows that waiters and waitresses in the US get lousy wages. It’s one of the reasons people usually try and remember to give them a tip.

One couple in Arizona certainly bore that in mind when they gave a heavily pregnant waitress a Christmas gift of $900.

Sarah Clark, a waitress and bartender at the Pita Jungle in Phoenix, received the tip from a couple she had served before when they came back for another meal.

Sarah Clark said her fiance was about to undergo surgery (CBS)

Their bill came to $61.30 and the standard tip of 20 per cent would have brought the total to $73.56. But instead they left her $961.30 - a tip of around 1,470 per cent.

On the bill, the couple wrote: “This is God’s money - he gave it to us so we could give it to you. God bless.”

“I couldn’t believe what I was looking at first because it was such a high amount - $900 is a lot of money,” Ms Clark told CBS. “And it took a while for it to set in, and once it did, I cried for a little while.”

Ms Clark, who is nine-months pregnant, said that her fiancé is due to go in for surgery this week and will be unable to work for some time. In January, she herself will go on maternity leave and they expect money to be tight.

She said the couple, who have not been identified, could little know how much the money means to her.