A US waitress was left overwhelmed by the sweet generosity of one customer who showed his appreciation for her service by leaving a massive tip.

The unidentified waitress at mac’s Grub Shack in Tennessee posted the image of the receipt and her tip on Imgur where it was picked up by a Reddit user.

“This guy sat in my section tonight & left a note on the back of his receipt,” she wrote above the photograph showing the receipt, which has now been viewed almost one million times.

On it, the mystery diner had written: “Today is my brother’s b-day. He would have been 36 today. Every year I go eat his favourite meal (hot dogs) and tip the waitress his age.

“Happy B-Day Wes,” the note ends.

After the image was posted on Reddit, one user flipped the image and increased the contrast to read what the mystery tipper ate.

His total bill (including sales tax) came to $29.50 – mean his tip of $36 was 100 per cent more than the bill itself.

The image has been greeted with delight online, with many Imgur users discussing their own ways of commemorating the dead and celebrating the mystery man’s actions.