Colorado will repeal sales taxes on marijuana Sept. 16, thanks to a quirk in its constitution.

The one-time-only holiday from the 10 percent state sales tax on recreational pot is likely to generate buzz in the first state in the nation to legalize marijuana.

The little-noticed provision is part of a larger bill that Gov. John Hickenlooper signed into law Thursday that includes a ballot initiative in November and a permanent tax cut on recreational pot sales in 2017.

“This fiscal glitch that we have with the constitution … that’s part of the magic of living in Colorado,” the Democratic governor said.

The impetus is the Taxpayer’s Bill of Rights, a measure championed by conservatives. The constitutional provision requires voters to approve new taxes based on estimates of collections and state spending. If the actual amount exceeds the estimates, refunds are necessary.

Colorado isn’t collecting more pot taxes than expected — actually, the amount is far less than projections — but total state spending exceeded initial estimates because of the improving economy.

“This is only a first-year problem,” said Sen. Pat Steadman, D-Denver, who authored House Bill 1367. “We’ll never have this problem again.”

When triggered, TABOR also requires the tax rate to be cut to zero. State lawmakers agreed to eliminate the sales tax for one day to meet the constitutional obligations and then restore it. The tax holiday is expected to cost the state about $100,000 in revenue. The bigger price tag — $3.6 million — is what the state anticipates losing in revenue for a one-day elimination of the 15 percent excise tax on marijuana sales from cultivators to retailers.

A permanent sales-tax break on recreational marijuana takes effect July 2017, lowering the rate from 10 percent to 8 percent.

“We still have a black market, and we want to moderate our taxes to make sure that the risk of someone selling illegally. … We want to eliminate that,” Hickenlooper said. “And one way is to make sure there is not as large a price differential.”

The focus of the bill, however, is the ballot question this fall. The state will ask voters’ permission to keep the estimated $58 million in pot taxes collected this fiscal year.

“This is one of those cases that we have to go back to voters and ask them if we can keep the money they already asked us to collect,” Hickenlooper said.

Mike Elliott, the executive director of the Marijuana Industry Group, a leading advocate, said in a recent interview that his group has not yet decided whether to take a stance on the ballot measure.

Unlike the initial ballot measures that legalized marijuana in Colorado, this November’s referendum isn’t expected to generate much attention. The governor said he would spread the word as he travels the state for town hall forums this fall and will rely on state lawmakers to help push the message.

The question is designed to give voters a stark choice about the money. If they agree to let the state spend it, the first $40 million will go toward school construction. The remainder is apportioned to a variety of marijuana programs for youth mentoring, agriculture, drug treatment and enforcement.

If voters reject the measure, the state will refund the bulk of the money — $33 million — to marijuana growers and users through tax breaks on production and sales. The remaining $25 million will go to all Colorado taxpayers through a sales tax refund.

The state already is planning a $70 million TABOR refund at next year’s tax filing, but it is separate from the marijuana tax rebate.

“We constructed this in such a way so voters will understand what happens when they vote yes and what happens when they vote no,” Steadman said. “The consequences of your yes or no vote are really clear.”

The Sept. 16 date was selected for the tax holiday because the end-of-the-year fiscal report is certified the previous day.

The date is also Mexican Independence Day, which marks the start of the country’s war against the Spanish colonial government. The word “marijuana” is considered offensive and racist to some Mexicans.

John Frank: 303-954-2409, jfrank@denverpost.com or twitter.com/ByJohnFrank