The Inland Revenue has started sending the first batch of more than 2.5 million automated tax statements that tell people whether they have a tax refund or a bill to pay.
Deputy Commissioner Sharon Thompson said the refunds will be going out in batches rather than all at the same time and warned people to look out for scams.
"We'll be contacting customers to let them know about their assessments by email or through a letter in the post.
"The main thing to remember is that if you have any doubt about whether that communication is genuine, then type ird.govt.nz into your browser and access our secure online services portal myIR from there. If you don't have a myIR account, then it's a good idea to register for one, as that's where all your information is securely displayed.
"There could be scammers out there trying to direct you to other websites so we encourage everyone to be vigilant. If you make your own way to ird.govt.nz, you can be sure you're in the right place."
The automated service comes less than a week after an Auckland woman was shocked when she opened her bank account to find $12 million had been deposited by Inland Revenue.
Ms Thompson says an estimated 1.65 million New Zealanders are likely to have a refund against their name – around seven times more than the number who will receive a bill.
"Most customers will see that money deposited straight into their bank account and won't have to lift a finger.
"After receiving an assessment, we expect it will take up to two days before any refund reaches a customer's account."
Latest estimates show that around 240,000 customers can expect to receive a tax bill and that may come as a surprise to customers who haven't had one before. They will have plenty of time to pay with a due date of 7 February 2020 or they can set up an instalment arrangement.
Ms Thompson says automatic tax assessments are part of Inland Revenue's plans to make tax more straight forward.
"We expect the amount paid out annually in refunds and the number of bills to pay will decline over the coming years as we now have a system that can recognise when someone is over- or under-paying tax and can help customers correct that."