Over a year after California voters opted to legalise recreational marijuana use, lawfully operated cannabis businesses are set to open.

In the interim, various state agencies and local governments have been working on crafting rules governing how the product is grown, where it can be sold and a host of other issues.

Now it's time for the long-informal industry's formal debut.

Here's what you need to know with recreational sales poised to begin in less than a week.

When does it come into effect?

In one sense, the law has already been in effect by removing penalties for possessing and growing cannabis. Even before Proposition 64 passed California had already steadily loosened the legal repercussions, downgrading possession of less than an ounce to an infraction generally punishable by a fine.

But the bigger change is that legal sales are set to commence in the new year.

The state issued its first batch of 20 licenses for retailers, distributors and testing labs earlier this month, at which point about 1,900 users had registered with the state's new processing system and more than 200 had formally applied.

The number of licenses issued has since risen to more than 160.

In pictures: 4/20 Marijuana world rallies Show all 26 1 /26 In pictures: 4/20 Marijuana world rallies In pictures: 4/20 Marijuana world rallies A man wears a marijuana leaf mask during the annual 4/20 cannabis culture celebration at Sunset Beach in Vancouver, British Columbia AP In pictures: 4/20 Marijuana world rallies A lady smokes marijuana on Parliament Hill on 4/20 in Ottawa, Ontario Getty Images In pictures: 4/20 Marijuana world rallies James Reed smokes a joint during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies People sign a 4/20 sign on Parliament Hill on in Ottawa, Ontario Getty Images In pictures: 4/20 Marijuana world rallies A woman smokes marijuana on Parliament Hill on 4/20 in Ottawa, Ontario. Polling released showed strong support in Canada for a government drive to legalise recreational use of marijuana, but many would like the proposed minimum age for consumption to be raised. Sixty-three percent of respondents told the Angus Reid Institute they support legalisation Getty Images In pictures: 4/20 Marijuana world rallies A man smokes marijuana during the annual 4/20 marijuana rally on Parliament Hill in Ottawa, Ontario, Canada Reuters In pictures: 4/20 Marijuana world rallies Demonstrators smoke marijuana during the '4/20 Santiago' rally in favour of legalisation in front of the La Moneda presidential palace in Santiago, as part of the Global Marijuana March which is being held in hundreds of cities worldwide Getty Images In pictures: 4/20 Marijuana world rallies People play with a mock marijuana joint during a 4/20 party to demand legalisation and to celebrate marijuana culture outside the Senate building in Mexico City, Mexico Reuters In pictures: 4/20 Marijuana world rallies Adam Eidinger, co-founder of DCMJ, hands out free marijuana joints to DC residents who worked on Capitol Hill as part of the 1st Annual Joint Session to mark '4/20' day and promote legalising marijuana on Capitol Hill in Washington, DC Getty Images In pictures: 4/20 Marijuana world rallies In pictures: 4/20 Marijuana world rallies Police arrest Rachel Ramone Donlan after she handed out free marijuana joints to DC residents who worked on Capitol Hill as part of the 1st Annual Joint Session to mark '4/20' day and promote legalising marijuana on Capitol Hill in Washington, DC AFP/Getty Images In pictures: 4/20 Marijuana world rallies Police arrest Rachel Ramone Donlan after she handed out free marijuana joints to DC residents who worked on Capitol Hill as part of the 1st Annual Joint Session to mark '4/20' day and promote legalising marijuana on Capitol Hill in Washington, DC Getty Images In pictures: 4/20 Marijuana world rallies Thousands of people gather to smoke marijuana during the '420 Santiago'rally in front of the La Moneda presidential palace in Santiago Getty Images In pictures: 4/20 Marijuana world rallies People attend the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies Kevin Barron and Lasean Moore of Raleigh, North Carolina, share a joint during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies Nic Ruhl takes a pull on a giant hand rolled joint at precisely 4:20pm MDT during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies Various cannabis paraphernalia on display at a vendor's stall during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies Mo Banez, of Austin, Texas, lights a joint during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images In pictures: 4/20 Marijuana world rallies A man displays a large container of cannabis during the Denver 420 Rally at Civic Center Park in Denver, Colorado. The rally, held annually, is a celebration of both the legalisation of cannabis and cannabis culture. Colorado is one of twenty-six U.S. states along with the District of Columbia that has legalised the use of cannabis either recreationally or medically AFP/Getty Images In pictures: 4/20 Marijuana world rallies Sitting in small groups on mats shaded by trees in the Rose Garden just across from the Knesset, participants lit up as the clock struck 4:20 for the local version of the traditional worldwide April 20 pro-marijuana events, known as '420' rallies Getty Images In pictures: 4/20 Marijuana world rallies An Israeli smokes a marijuana joint in Jerusalem during a rally at the Rose garden Getty Images In pictures: 4/20 Marijuana world rallies Sitting in small groups on mats shaded by trees in the Rose Garden just across from the Knesset, participants lit up as the clock struck 4:20 for the local version of the traditional worldwide April 20 pro-marijuana events, known as '420' rallies Getty Images In pictures: 4/20 Marijuana world rallies An Israeli girl poses with a mock marijuana joint in Jerusalem during a rally at the Rose garden, to celebrate 420 and to express their defiance of current laws Getty Images In pictures: 4/20 Marijuana world rallies aelis pass around a marijuana joint in Jerusalem during a rally at the Rose garden, to celebrate 420 and to express their defiance of current laws Getty Images In pictures: 4/20 Marijuana world rallies An Israeli smokes a marijuana joint in Jerusalem during a rally at the Rose garden, to celebrate 420 and to express their defiance of current law Getty Images In pictures: 4/20 Marijuana world rallies An Israeli smokes a marijuana joint in Jerusalem on April 20, 2017 during a rally opposite the Knesset to celebrate 420 and express defiance of current laws AFP/Getty Images

Where can I buy it?

Whether or not pot shops open on your corner depends in part on where you live. The law preserves local control over permitting, meaning counties and cities reserve the right to restrict where cannabis can be sold or ban it outright.

Both San Francisco and Los Angeles passed rules governing pot shops after contentious fights that involved concerns about public safety, blight and quality of life.

Kern County, which sits in California’s more conservative rural heartland, has prohibited sales altogether.

What will still be illegal?

Authorising recreational marijuana doesn’t mean a legal free-for-all. Various marijuana-related activities are still against the law.

Transporting the product across states lines, for example, remains a felony. Individuals can grow their own, but no more than six plants. Public consumption is still not allowed and you have to be 21 to buy it.

Driving while stoned is also forbidden, although the state faces questions about how California Highway Patrol officers would test for intoxication given that traces of marijuana can remain in the body long after a high fades.

How is it taxed?

Because it will be treated like a more conventional retail item, marijuana will be subject to sales taxes when you buy it.

How much tax you pay will depend on where you are in the state, since localities have some control over how much it is. Medical marijuana is exempt from the sales tax.

On top of that, the law also imposes a 15 per cent excise tax on purchasers of marijuana products, which retailers have to collect and pay to their distributors. Pot farmers will also face taxes on their crops: $9.25 (£6.97) per ounce of flowers and $2.75 (£2.04) per ounce of leaves.

Taxes may seem like a dull subject, but they strike to the heart of the delicate balance in setting up a legal pot market.

Voters were sold on the idea in part, because of the additional tax revenue flowing from a newly regulated industry.

Collecting those taxes is part of a bigger way — in addition to handing out licenses and imposing rules on transport, the environment and testing — to legitimise pot businesses.

However, experts say you want the price to be competitive enough that legal pot competes with and undercuts the black market. If taxed too heavily, there is the risk people will keep buying from cheaper, illicit suppliers.

How will current farmers be affected?

For years, this question has loomed over California’s efforts to regulate its sprawling medical marijuana marketplace and the push to legalise the plant in general.

The state owes its longstanding position as the epicentre of America’s pot economy in large part to the small-scale growers who have tended their crops in the rugged forests of the “Emerald Triangle,” a trio of pot-growing counties, and other parts of the state.

Of course, it’s not all small farms: cartels and large-scale criminal enterprises are also operating. Plenty of small-scale growers say they want clearer rules so they can distinguish themselves from the bad guys and grow in a way that’s safe for consumers and respects the environment.

Those farmers can now grow and sell cannabis in the open, without fear of raids. But there are real concerns about whether they’ll survive.

Along with the new taxes, farmers will have to spend money to get their properties up to code and conduct testing to ensure the product is safe.

As a result there are widespread worries that onerous local zoning and permitting requirements will make it prohibitively expensive or difficult for folks used to informal businesses to get their pot into the legal market.