An eagle-eyed Coles shopper has pointed out a virtually unknown fact about the supermarket's popular hot roast chicken vouchers.

The vouchers allow customers to collect a voucher for a free hot chicken if none are currently available in store.

The voucher states that it must be used within seven days of the date it was issued and isn't valid at Coles Express or via Coles Online.

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However, the shopper pointed out that it's important to check the sticker advertising the promise on the hot chicken display at their local Coles.

The sticker tells customers the times the voucher is valid between and they're different at every store.

This dedicated shopper went to different Coles to prove their point.

At one supermarket, the sign states: “If you’ve missed out on a Coles hot roast chicken between 9 am to 8pm, your next one is FREE.”

At another Coles, the sign indicates that the promise is only available between “11 until close”.

The shopper warned other customers to be aware of the differences before asking for the free voucher.

“Just make sure you check the sticker on the display before asking for a free voucher,” said the shopper.

“If you’re there before or after the times that are indicated then you aren’t eligible for a free hot chook.”

Photo credit: 7News

This article originally appeared on Over60.