It's the first tax deadline for the first fully regulated marijuana market in the world.
Colorado pot sellers have until the end of Thursday to report January sales taxes to the state Department of Revenue. The total will give the first glimpse at the size of Colorado's new recreational marijuana market, though results won't be made public until early March.
Colorado charges a 12.9 percent sales tax on recreational pot, plus an additional 15 percent excise tax. The first $40 million from the excise tax will go to school construction.
The remainder is fair game for state budgeters. Gov. John Hickenlooper has already released his proposal for spending some $99 million in pot tax money next year.
Colorado has 163 licensed recreational pot shops.