A young traveller has expressed her frustration after she copped a $2,664 fine for failing to declare her Subway sandwich.

Jessica Lee, from Perth, bought a foot-long Subway at Singapore airport while waiting for her flight home to Australia.

After she ate six inches of the sandwich, the 19-year-old decided to save the other half for her flight.

But she ended up not eating the rest during the journey home.

Upon presenting at Australian Customs, she was given a hefty fine - because she didn’t declare two ingredients in her sandwich - chicken and lettuce.

“Probably will cry. Basically just paid $2,664 for my Subway just from Singapore,” Jessica said in a TikTok video.

“It is my mistake but basically I bought a foot long Subway at Singapore airport because I was a hungry girl after my 11-hour flight.

“I ate six inches before my second flight and then saved the other six inches for my flight, which they [cabin crew] were more than happy with, they were fine with that.”

Struggling to hold her anger in, Jessica said things didn’t go to plan when she landed in Australia.

“I didn’t eat it on the plane,” she explained.

Jessica said she didn’t declare her food because she assumed the form only applied to pre-purchased items in carry-on suitcases and check-in luggage.

“I didn’t tick chicken and I didn’t tick lettuce. Chicken and lettuce,” she said.

“And that is a nice little $2,664... to be paid in 28 days.

“Such an expensive rookie mistake.”

Rubbing salt into the wound, Jessica appeared defeated as she revealed she was unemployed after she quit her job to go on her European trip.

“I have rent to pay,” she said.

Jessica added: “I am very aware this is my mistake and I do take ownership, I am paying the fine.”