As a second round of stimulus checks makes its way to millions of Americans, many people may be wondering whether or not they'll receive one.

For the most part, those who received a $1,200 check earlier this year will likely receive a $600 stimulus check this time around. However, there are a few differences between this round of payments and the first one. And in some cases, those who were eligible for the previous check may not qualify for a second payment. Here are three key reasons you may not receive a stimulus check.

Check from the United States Treasury

Image source: Getty Images.

1. You make too much money

Under the CARES Act earlier this year, you qualified for a stimulus check if your adjusted gross income (AGI) was under $99,000 per year (or $198,000 per year for those who are married and filing taxes jointly). Under the new relief bill, the income limits are slightly lower.

The most you can receive is $600 (or $1,200 for those who are married and filing jointly). If you earned more than the income limit for the full payment, though, you'll either receive a reduced payment or nothing at all. Because the income limits are lower with this round of payments, you may not qualify for a check this time even if you received the first stimulus check.

Filing Status AGI to Receive Full Payment AGI to Receive Partial Payment AGI to Receive Nothing
Individual $0 to $75,000 $75,001 to $87,000 $87,001 or more
Head of Household $0 to $112,500 $112,501 to $124,500 $124,501 or more
Married Filing Jointly $0 to $150,000 $150,001 to $174,000 $174,001 or more

Data source: IRS.

So, for example, if you're an individual filer earning $90,000 per year, you would have qualified for a reduced stimulus payment under the CARES Act. This time, though, you won't receive anything.

The caveat is if you have children age 16 or younger. You can receive $600 per qualifying dependent, even if your income surpasses the income limit. So although you may not qualify for your own check, you could still receive a stimulus payment in some cases.

2. You don't have a Social Security number

Similar to the CARES Act, those who do not have a Social Security number are excluded from this round of stimulus checks. However, there is an important change under the new relief bill.

With the first round of stimulus payments, if one spouse was a U.S. citizen and the other was not, neither could collect a stimulus check. Under the new bill, however, "mixed-status" households are eligible for checks. If only one spouse has a Social Security number, the other can still receive a check. But in order for both spouses to receive a check, both need to have Social Security numbers.

3. You're claimed as a dependent

Under the new relief bill, households with children can receive an additional $600 per qualifying dependent. However, under the tax law, "qualifying dependent" refers to children age 16 or younger. That means those who are age 17 or older and listed as a dependent on someone else's tax return do not qualify for a stimulus check.

This rule has remained unchanged since the CARES Act, and it means millions of teens, college students, individuals with disabilities, and seniors who are claimed as dependents do not qualify for stimulus payments.

While stimulus payments may come as a relief to the millions of Americans who have been struggling financially due to the COVID-19 pandemic, not everyone can expect to receive one. If you fall into one of these three groups, you may not qualify for a payment this time.