Retailers are being warned they are being watched by the country's consumer watchdog.
The Competition and Consumer Protection Commission says it is already monitoring prices being charged, to ensure that winter sales offer legitimate price reductions.
It comes as new rules were introduced last year on price reductions.
By law, when a business makes price reduction announcements, they must display the lowest price a product was on sale for in the previous 30 days, and base the discount on this price alone.
Kevin O'Brien, member of the Competition and Consumer Protection Commission, says retailers discounts must be genuine:
"It's all about being in line with consumers and being fair to consumers. Value for money is a huge issue at the moment. Consumers want to know they're getting real value when they buy something on Black Friday, 0n Cyber Monday, in the January Sales. Our message to consumers is always to ask themselves 'What is the value to them of the product they're thinking of buying?'"
