You can still collect money from your 2019 tax returns—the average refund is $893

Hundreds of dollars from the Internal Revenue Service could be up for grabs if you haven't submitted your 2019 tax return yet.

A whopping $1.5 billion in tax refunds remain unclaimed from the 2019 tax season, with the average refund totaling $893, the IRS says. You'll have to file by July 17 to get your cut — a later deadline than usual, due to pandemic-related extensions.

"It doesn't make sense to leave money on the table," says Riley Adams, a certified public accountant and founder of the financial literacy website Young and the Invested. If you weren't required to submit a tax return for that year, you might not realize the IRS could still owe you cash, he says.

Some people are eligible for an even larger payout: up to $6,557, if you qualified for the Earned Income Tax Credit (EITC).

Here's what you need to know about the ETIC and other notable tax credits, and which forms you'll need to file a 2019 tax return.

Reasons for filing your 2019 tax return

If you didn't make much money in a given year, you aren't required to file a tax return. That threshold for 2019 — known as the standard deduction — was $12,200 for single filers and $24,400 for joint filers.

But even if you didn't need to file a return, your employers might still have overpaid on your taxes, putting you in line for a refund.

You may also be able to claim some refundable tax credits, which are paid out as cash if they exceed the amount of money you owe the IRS. Many tax filers qualified for the EITC, a credit for low- to middle-income earners who earned less than $50,162 for single filers, or $55,952 for joint filers, in 2019.

Unfortunately, the IRS' interactive eligibility tools for the 2019 tax credits are no longer active, but you can check if you'd qualify for the EITC on this IRS webpage. 

"About 20% of the people who are eligible for the earned income tax credit each don't claim it," says Adams, citing IRS data.

Those people could be missing out on a lot of money. For 2019, these are the maximum Earned Income Tax Credit (EITC) taxpayers can claim:

• $529 without qualifying children
• $3,526 with one qualifying child
• $5,828 with two qualifying children
• $6,557 with three or more qualifying children

You might also qualify for a partially refundable child tax credit, which pays $2,000 for each eligible child. You can receive the full credit for 2019 if you made less than $200,000 as a single filer, or $400,000 if you're filing jointly.

For every $1,000 of income over those thresholds, the credit is reduced by $50, for both single and joint filers.

And look out for the American Opportunity Credit for school-related expenses incurred in your first four years of post-secondary education. It's 40% refundable, and its maximum credit is $2,500 per student. You can learn more about its eligibility requirements on the IRS website.

The IRS is only accepting mailed 2019 tax returns, so you'll need to send your tax return to the addresses listed on this IRS webpage. If you use tax software, you can print out your finished tax return and mail it the the IRS directly, says Adams. (To learn about the best tax software options, see CNBC Select's list.)

You could also hire a tax specialist to prepare and file your tax form on your behalf. And if you lost track of 2019 financial records like W-2s and 1099s, you can access them using the IRS transcripts webpage.

Tax forms for 2019 are accessible on the "Prior Year Forms and Instructions" IRS webpage or by calling 1-800-TAX-FORM.

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