The stores offered reusable bags, a thicker 15-cent plastic bag - designed to be used 20 times - and the $1 Bag-For-Good for those who did not have their own bags.
All Countdown stores in Ashburton, Napier, Hastings, the Waikato region, Auckland's North Shore and Timaru would also make the move away from plastic on October 8.
Hannifin said having the entire South Island network phase out single-use plastic carrier bags was a massive milestone for the business.
"[It] will mean every one of our South Island Countdown stores is supporting customers to make the move to reusable bags. The end of single-use plastic bags at our checkouts and online is in sight."
Customers were adapting well to the changes and adjusting their shopping habits, even in stores where bags are yet to be phased out, Hannifin said.
"Already, we have seen a 17 per cent decrease in the amount of plastic bags our customers are using when they shop with us.
"Making reusable bags the norm will have long-lasting benefits for New Zealand's environment.
"One of the reasons the phase out is going so well is that our customers have really got behind this move and we hope this will continue when these further stores make the change."