An eagle-eyed Woolworths shopper has revealed a relatively unknown hack that can save hundreds off your Christmas shopping food bill.

The hack was shared on a popular Facebook page, with one shopper showing that Woolworths Rewards members have the option to bank their savings until later in the year. 

“Just in case you didn’t know, you can bank all your [Woolworths Rewards] savings for Christmas time,” wrote one Woolies shopper on the Markdown Addicts Australia page.

“When you get [money] from your Rewards card, you can bank it until December when it will become available. A little saving tip for that crazy Christmas time.”

Users of the Woolworths rewards card are thrilled with the option, with some already cashing in on the savings.

“It’s so good, I have $200 for Christmas so far,” said one.

Added another: “We have $600.”

Benefiting from the savings is easy as you simply change the settings when you select "Bank for Christmas" in "redemption settings" under "my account". 

The change is even easier to do if you're using the Woolworths Rewards app, as your preference is shown under the welcome banner on the home screen.