If your share of the $3 billion that the Massachusetts state government is returning to taxpayers hasn’t hit your bank account or mailbox yet, keep checking.

After the state collected enough revenue to trigger a little-known 1986 law capping the annual growth in tax collections, the Massachusetts Department of Revenue announced that the excess money would start flowing in November to people who had filed income tax returns in 2021.

The refunds are automatic, with no action required by the taxpayer. If you included bank information on your 2021 tax return, you'll get your refund by direct deposit, labeled "MASTTAXRFD." Otherwise, it'll come via a check in the mail. The checks will include a short explanation of the tax-cap law and why the refund is being issued. If your address has changed since filing your 2021 taxes, the Department of Revenue advises updating your address on the MassTaxConnect portal to make sure the checks find you.

The Department of Revenue started sending out the money on Nov. 1, with plans to distribute around 500,000 refunds that week. In all, about 3 million taxpayers are expected to receive refunds, and the state says they should arrive by Dec. 15 for people who have already filed their 2021 taxes. Anyone who hasn't yet filed last year's taxes will be able to get a refund if they file by Sept. 15, 2023. Refunds for eligible late filers will land about one month after filing. Residents, non-residents and partial-year residents are all eligible if they paid Massachusetts income taxes for 2021.

The refunds aren’t a uniform amount; people will get back 14% of what they paid in state income tax in 2021, after accounting for any credits. The Department of Revenue has an online refund estimator tool, and you’ll need your 2021 tax return handy to fill it out. Married couples who filed jointly will receive one refund. Unpaid taxes, unpaid child support and other debts could reduce an individual’s refund amount below what’s projected.

There’s no system to check the status of the refunds, so it’s a matter of waiting for them to arrive. A call center, which will not provide exact refund amounts, is open Monday through Friday from 9 a.m. to 4 p.m. to field refund questions at 877-677-9727.