Consumers who buy an item only to see it go on sale within the next seven days will be refunded the difference under a new business accreditation scheme.
Power and mobile phone network vendors are among retailers prepared to put their reputations on the line by joining the scheme where businesses will be vetted and approved by Consumer NZ.
The consumer rights watchdog has so far accredited four companies for its new Consumer Trusted programme.
Each had to show high standards for returns and refunds, websites, customer privacy and fair and clear pricing.
One of Consumer's measures is if a product worth over $100 goes on sale within a week of you buying it, you are entitled to a refund of the difference.
"We've thought hard about how to raise the game of Kiwi businesses," said Consumer NZ chief executive Sue Chetwin.
"Our advisory service deals with around 4000 complaints and inquiries each year - and that's just the tip of consumer dissatisfaction."
Ms Chetwin said the aim was to inspire businesses to go beyond the minimum standards required by consumer law.
Although businesses paid a fee in order to be considered for accreditation, Ms Chetwin said Consumer NZ would remain "absolutely independent" and its research and testing work on behalf of all consumers would not be influenced.
Signed up so far as "trusted" businesses are Powershop, a Wairarapa-based online power company, 2Degrees mobile phone network; internet service provider Inspire Net and Shoe Clinic, with 18 stores in its footwear and clothing franchise.
Powershop chief executive Ari Sargent said he understood that Consumer NZ would periodically audit the company's service standards.
"They will keep us honest on our claims," he said.
Shoe Clinic managing director Neville McAlister said the company was already observing the code of conduct for customer service, including a 30-day money-back guarantee if customers were unhappy with goods.
NZ Retailers Association Auckland regional manager Russell Sinclair said this was not a common practice but customers were becoming increasingly savvy and retailers were giving them a reasonable hearing.
He said it was a commercial decision for businesses to pay for accreditation, if they thought it would get them a competitive advantage.
"But everybody in retail is looking for a point of difference and advantage and they are also looking after their customers - many of them exceed consumer and fair trading laws requirements."
New Zealand had 32,972 retail outlets in 2013 and annual sales topped $70 billion.
Principles of Trust
• Provide excellent customer service.
• Fair, clear returns and refunds policies.
• Informative and up-to-date website.
• All complaints and disputes dealt with fairly.
• Contracts must be fair and easily understood.
• Clear pricing.
• Customer details are not exploited.
• Advertising is accurate.