The ninth installment of the third round of stimulus checks, totaling more than $1.8 billion, will reach the bank accounts and mailboxes of nearly one million Americans this week.

Following the passage of the Biden Administration's American Rescue Plan, the IRS has been processing payments weekly since mid-March. This latest round includes full stimulus checks (up to $1,400) for more than 500,000 individuals who did not have enough information on file to qualify for payments before filing their 2020 tax returns.

An additional 460,000 individuals received "plus-up" payments. This is a supplemental check for taxpayers who qualify for more relief based on their 2020 income, but whose initial payment was calculated on their 2019 tax return. This includes those who had less income in 2020, got married, or had more dependents.

The IRS reports that more than 6 million supplemental-up checks have been distributed. So far, stimulus checks3 have been issued to 165 million people, totaling approximately $388 billion.

Those who have not yet received Stimulus Check 3 must file their 2020 tax returns. This is usually the best way to claim your relief check, even if you do not file a tax return.

The IRS encourages people who are disabled, living on pensions, Social Security, homeless, or have little or no income to file this year. The IRS pays them when they process their returns.

The deadline to file is Monday, May 17. However, according to CNBC, if you file for an additional extension and wait to file until October 15, you are still eligible to receive a check.

The IRS also allows taxpayers to use their 2020 income to claim additional deductions for stimulus checks 1 and 2. Again, this is an opportunity for those whose 2020 income was less than their 2019 income to get more; the Recovery Rebate Credit is found on Form 1040 and Form 1040-SR, line 30.

If qualified, the credit is received as a refund or applied to taxes owed.

Depending on your income level, you may qualify for assistance in completing and filing your 2020 tax return. Those with income up to $72,000 may qualify for assistance from IRS Free File partners. Those with incomes below $57,000 may be eligible for more in-depth tax preparation assistance through the Volunteer Income Tax Assistance program.

Taxpayers with incomes of $72,000 or more may file electronically using the IRS's free fillable form (no guidance provided).