Chang, a motel operator, had been taking advantage of several in-store specials on Wednesday, buying six packs of toilet paper, a dozen boxes of tissues, four litres of washing detergent and three toilet cleaning products.
He also bought some disinfectant spray, which was not on special.
All the items were for home use.
"I went in there, proceeded to check out and the manager said 'you're not a normal shopper. You're buying everything on special'. He said we can't serve you and asked me to leave."
Chang was too embarrassed to say anything in store, but later made a complaint with New World online.
"How I felt was, I was guilty from the start. I felt really uncomfortable. I felt like my money wasn't good enough for them.
"I've never been discriminated against like that," he said.
Chang, who moved from Taiwan to New Zealand more than 20 years ago, said he felt it was a case of racial profiling, but a New World spokeswoman denied this.
New World does not sell to traders, as the stores were not able to cope with the amount of stock trade customers needed.
"However in this instance, the customer was merely taking advantage of some attractive specials in store," the spokeswoman said.
"This has highlighted some procedural issues that the owner-operator intends to run over with his team, so that they know how and when to raise this question in future.
"There was no discrimination or racial profiling involved - it was a matter of staff needing a refresher on procedure, which the owner-occupier will quickly rectify."