April 15 is not tax day in 2021, but it’s still a crucial deadline for some taxpayers — are you among them?

Now, taxpayers face a unique series of deadlines that may or may not apply, depending on what they do for a living and where they live.

Also, though, yes, April 15 is a crucial deadline from some taxpayers.

In the face of this abnormal, easily confusing and highly important tax season, when people need to be sure they are getting back every last income-tax dollar they deserve and paying no more than their fair share, MarketWatch has compiled a list of the key dates from here out.

April 15: The first installment of estimated payments for 2021 are due.

Most taxpayers pay their income taxes, Social Security and Medicare taxes when their employer withholds taxes on their paycheck. Gig workers, independent contractors, sole proprietors and other self-employed individuals have no employer, so they’ve got to pay the taxes themselves. That happens through estimated payments, which are sliced into four installments per year.

Though the IRS postponed the income-tax-filing date for the 2020 tax year, it kept the estimated-payment schedule intact for 2021 and has received some criticism for not extending this deadline as well. In addition to April 15, estimated payments for this tax year are due on June 15, Sept. 15 and Jan. 18, 2022.

May 17: 2020 federal income-tax returns are due, as well as taxes owed.

Monday, May 17, marks the date when taxpayers have to submit their 2020 tax return and pay any taxes owed. The 2020 return is a taxpayer’s final opportunity to claim missed-out-on stimulus-check money from 2020. A taxpayer receives the money through the “Recovery Rebate Credit,” and the money gets lumped into a person’s refund, or is paid in that manner if no refund would otherwise be forthcoming.

Here’s a longstanding caveat on the filing deadline: A taxpayer can receive an extension up to Oct. 15 to file an income-tax return. But if they owe taxes, the filing date is still the last day to pay without penalties and interest. If someone is unable to fully pay by the deadline, the IRS offers installment plans.

May 17 is the last chance to shrink your 2020 tax bill through contributions to an IRA or Health Savings Account, and it’s also the final chance to file a 2017 return and claim a refund for that year.

Bear in mind that the May 17 deadline only applies to federal income taxes. States may have also copied the IRS and pushed back deadlines for their income-tax returns, but those dates will vary. As of earlier this week, 36 states had pushed their tax deadlines to May 17, according to a list compiled by the American Institute of Certified Public Accountants.

The IRS had received 93.2 million returns as of April 2. The average refund has been $2,893.

Beginning in May: Start of refunds based on returns readjusted for the March relief legislation.

The $1.9 trillion American Rescue Plan passed in March included a valuable tax break for people who received unemployment benefits during 2020. The relief bill said the first $10,200 received in benefits is not subject to federal income tax. The income-tax exclusion applies to households making less than $150,000 a year. The exclusion is $20,400 for married couples filing jointly.

By the end of February, there were 5.4 million people who had already filed returns and could have benefited from the exclusion had it been on the books, according to IRS estimates. The IRS is automatically recalculating those returns and in May will start sending any extra refunds based on those readjustments. The payments will be sent out through December.

A readjusted return calling for more refunded money is welcome news, but taxpayers might want to see if the readjustment puts them in a position to claim even more tax money through an amended tax return.

June 15: Federal income-tax filing deadline for Texas, Louisiana and Oklahoma residents.

In the wake of a February’s devastating winter storm, which sent temperatures plunging and utility bills soaring, leaving many without power, heat and even water for a lengthy stretch, notably in Texas, the IRS pushed back the filing deadline for residents and businesses in these three states. The June 15 deadline also pushes back the estimated payments that taxpayers in this state would have otherwise paid on April 15, according to the IRS.

Louisiana and Oklahoma’s state income-tax deadlines this year have been extended to June 15. Texas has no state income tax.

Beginning in July: Payments scheduled to begin for expanded child tax credit.

Apart from the tax break on jobless benefits, the American Rescue Plan also temporarily boosted payouts under the child tax credit. The credit is now up to $2,000, and $1,400 can be layered into a refund. The relief bill boosts the payout to $3,000 per child, and the age limit now encompasses 17-year-olds. It also pays $3,600 for children under age 6. The credit is completely refundable, too.

In addition to increasing the credit’s value, the bill said the IRS can advance those payments, starting in July, instead of paying families in a lump sum next tax season.

The IRS is working on an online portal where taxpayers can opt out of the advance payments or submit information on a household change, like reporting the birth of a child.

IRS Commissioner Charles Rettig said this week that the bureau is on track to send out monthly payments starting in July. “If we end up not being on track for some unforeseen situation, we will advise you and the committee,” he said during a Tuesday hearing, responding to a question from Sen. Sherrod Brown, a Democrat from Ohio.

At a congressional hearing in March, Rettig said the IRS needed people to file their tax returns so the tax-collection agency knew where to send payments.

Oct. 15: Deadline to file returns after receiving an extension.

This is it — the final deadline to submit a federal income-tax return after receiving an extension. The IRS notes that the way to seek an extension is by filing Form 4868. People can do this via their tax preparer or with tax software. It can also be accomplished through the IRS’s Free File Program.