Sales tax on marijuana in Colorado was so profitable last year - almost double the predicted amount - that the US state has declared a pot tax-free day.
Tax collected on marijuana sales came to $NZ110 million, much more than the $NZ62 million the state predicted.
The tax will return to 25 percent on Thursday, but state law requires an automatic suspension of any new taxes due to the accounting error.
Pot retailers are hoping for large crowds on the pot tax-free day.
Colorado became the first state in the US to legalise cannabis, after voters approved the change in 2012.
The average savings on Wednesday for a $NZ313 ounce of marijuana will be about $NZ30, and a regular 2.9 percent sales tax will still apply, as will taxes on medical marijuana.
The temporary tax break could cost Colorado up to more than $NZ6m in revenue.
"We've seen the numbers down the last couple of days in the stores," Tim Cullen with Colorado Harvest Company told the news channel.
"People waiting for the tax-free day. We're ready for it. The store is fully stocked and staffed. I think a lot of people will show up."