Differences between the House and Senate marijuana bills are being ironed out this week on Beacon Hill.

Both chambers last week passed their own bills calling for changes the recreational marijuana law passed by voters last November. Now a six-member conference committee made up of House and Senate lawmakers must reconcile the two bills.

In theory, the six conference committee members are the ones doing the negotiating. But in practice, much of the horse-trading will take place in back-channel discussions between the conference committee chairs and House and Senate leadership.

Both branches have indicated they want to have a bill on Gov. Charlie Baker’s desk by a self-imposed June 30 deadline — exactly a year and a day before retail sales of marijuana are supposed to begin. The compromise bill will have a major bearing on whether that July 1, 2018, date for sales can be achieved, or will be further delayed.

There are six major areas of the bills that need to be reconciled. In three of those areas — taxation, local option and expungement — there are considerable differences between the branches. In the remaining three — governance, safety/packaging and equity — the House and Senate are much closer and agreement is likely.

It is possible the conference committee could report out a partial bill on areas where there is agreement, and set the other, thornier matters for another time. Governance, that is the setting up of a regulatory agency, is of the utmost importance in terms of keeping target dates intact.

Taxation

There’s a great deal of difference between the House and the Senate when it comes to taxation. The Senate left the question of taxation exactly as the voters approved it in November at a maximum of 12 percent — 3.75 percent marijuana excise, 6.25 percent state sales tax, and an up to 2 percent optional local tax. The House has proposed raising the overall tax significantly to 28 percent — 16.75 percent marijuana excise, 6.25 percent state sales tax, and a mandatory 5 percent local tax.

Sen. Patricia Jehlen of Somerville, who is the Senate chair of the conference committee, has repeatedly said that raising the tax would keep the black market marijuana trade in business, since illegal sales would not be subject to the tax.

In defending the 28 percent tax last week during House debate, Rep. Mark Cusack of Braintree, who is on the conference committee and served as the House chair of the Marijuana Policy Committee, said it is better to aim high now and then lower the tax later if it is learned the tax rate has not eradicated the black market.

It is possible the House set the rate higher in anticipation of negotiating it down to a compromise figure during the conference committee. There had been an erroneous report just prior to the release of the House version of the marijuana bill that the tax would be set at 18.75 percent, which is close to the midway point between the House and Senate bills and could be the figure the House was hoping to settle upon.

Local Option

There is broad disagreement between the House and Senate with regards to the mechanism local communities can use to ban marijuana businesses from cities and towns. The Senate wants to keep the opt-out procedures as is — meaning if a city or town wants to ban marijuana establishments, the question must be put to voters in a referendum. This can be costly and cumbersome for communities, and many local leaders have been actively advocating for a more streamlined method, specifically allowing boards of selectmen or city or town councils to decide on their own whether their community will allow the businesses to set up shop within their borders.

The coalition that put the legalization question before state voters fear zealous local leaders will shut the door to marijuana businesses without regard to the citizenry. The House bill counters that the mandatory 5 percent local marijuana tax will make local leaders think twice before shutting the door to what has the potential to be a lucrative revenue stream, and so therefore going to the voters is not necessary.

Expungement

Senators want to include the sealing of many past marijuana criminal records in the bill, while the House feels expungement might be better dealt with at a later time — possibly if the Legislature takes up a more comprehensive criminal justice reform package later this session.

Expungement has been a priority for Sen. Jehlen, both relating to marijuana as well as other drug crimes that focused on possession rather than distribution. She has said now is the time to take up the issue.

During the run up to the release of the House bill, Rep. Cusack said expungement would be better handled by the Legislature’s Judiciary Committee. The fact that the Senate chairman of that committee, Sen. Will Brownsberger of Belmont, was appointed to the conference committee for the marijuana bill could be an indicator the Senate is not willing to back down on expungement.

Governance

This is the wonkiest part of the law, but is one area where the House and Senate have been pretty close from the get go.

The voter-approved marijuana law created a three-member Cannabis Control Commission which would operate under the state treasurer’s office, much like the long-established Alcoholic Beverages Control Commission. It would be up to Treasurer Deborah Goldberg to appoint the members and oversee the commission’s operation.

Both House and Senate leaders quickly criticized that set-up since it gave a lot of power to one official, and instead proposed a model of governance that would expand the commission from three to five members. It gives Goldberg, Gov. Baker and Attorney General Maura Healey one appointment each, with those three officials agreeing on the remaining two appointees. That model is very similar to the Massachusetts Gaming Commission, which was created by the Legislature in 2011.

Supporters of the marijuana referendum fear the five-member, independent board will not be limber enough to efficiently promulgate regulations and issue licenses to what could be hundreds or even thousands of marijuana-related establishments.

Safety/Packaging

Lawmakers in both the House and the Senate want to mark their territory now when it comes to marijuana safety and packaging, and not leave it to yet-to-be named regulators. Advocates of the law that was passed by voters have said regulations should be left to the Cannabis Control Commission, adding should the Legislature determine after those regulations are drawn up that they should be different they can then enact legislation stipulating what is prohibited and what is allowed. Both the House and Senate are in close agreement that marijuana products should be sold in child-safe, opaque containers, and that labels should not have cartoon characters or other packaging that appeals to under-age users.

Equity

This is an area of importance to the Black and Latino Legislative Caucus. They argued that the original House bill did not have assurances that minority-owned marijuana businesses would have a fair chance to get licenses to operate. They argue that in the past, minority communities have been disproportionately harmed by laws prohibiting marijuana, as well as by the enforcement of those laws. They want the state law to promote and encourage full participation by minority-owned businesses in the emerging marijuana industry.

Senior member of the caucus, State Rep. Byron Rushing of Boston, said Monday he is very pleased with the equity language that was inserted into both the House and Senate bills last week, and is confident an agreement can be reached between the branches.