The wheels for a third stimulus check are in motion, after President-elect Joe Biden introduced a $1.9 trillion stimulus proposal days before his Jan. 20 inauguration. In addition to $400 in weekly bonus to unemployment insurance and money for COVID-19 vaccine distribution, Biden's plan includes a $1,400 stimulus payment, which, when combined with the $600 maximum for the second stimulus check, brings the total per eligible adult to $2,000.

A $1,400 maximum would clearly bring household more money overall, so long as all other stimulus qualifications remain the same. But if they change -- as some would, in Biden's stimulus plan -- or your life circumstances alter, there are ways that some people could potentially get more money in a third check than they could in the second stimulus payment.

More dependents would qualify under Biden's plan

Who counts as a dependent? That depends on the definition in the future stimulus package. With the first and second checks, a dependent is any child aged 16 or younger, but previous proposals from Democrats -- and Biden's new stimulus plan (PDF) -- seek to expand the definition to include anyone you can claim on your tax returns -- such as children over 16 and adults under your care.

If passed -- and again, all of this is still in proposal territory for now -- that could bring a family $500 or $600 more per person you support, based on the per-child allowance outlined in the first and second checks, respectively. It isn't clear if there would be a cap on the number of dependents you could claim in this situation. 

A quick calculation: If you have one dependent who qualified in the first two rounds and three that qualify in the third, that would get your family $1,000 to $1,200 more if you have no other changes.

Could a child dependent count for more money this time?

Biden's stimulus plan has not yet sketched out how much money would apply to children, but his inclusion of dependents of any age signals that there would be additional money for this group in the next round.

A White House proposal from October offered to keep the same age restriction for children, but double the payout to $1,000. So in this specific and very hypothetical scenario, if you have one dependent, your third check could be $500 greater than the first check ($500 per child dependent) and $400 larger than the second ($600 per qualified dependent).

Do you have a brand new dependent?

If you had or adopted a new child, or if an older relative moves in, or if for whatever reason you gain a dependent since the last check, you may also see $500, $600 or $1,000 more, depending on the amount stipulated in the next (final) bill. It's likely the third stimulus check would use the figures from your 2020 taxes.

What if your employment status changes?

If you became unemployed this year or your wages dropped, that could lower your adjusted gross income, which is used to determine your payment. For example, if you got a partial payment with the first or second check, a third check could bring you a full payment if you're no longer employed.

Did you recently marry?

Depending on several variables that include your spouse's filing status and any new dependents, a change in marital status could result in a larger check. For example, if you were single and filing alone, you got $1,200 at most the first time around. Married, you could be eligible for up to $2,400, since the IRS formula used to determine your total stimulus money is based on your combined household income.

If a third stimulus check arrives for $2,000 per person, your spouse could double it to $4,000. Alternatively, if your personal AGI would only get you a partial stimulus check payment on your own, filing jointly with a spouse with an income under the threshold could qualify you for the whole check total.

You may newly share custody of a child

If you meet specific qualifications, you and the child's other parent may both be entitled to claim extra stimulus money. That means you could get an extra $500 or more in the third stimulus check, especially if anything in your situation changed between the time you filed your 2019 tax return and your future 2020 return. The third check allowance would be based on your most recent tax filing.

A rule change concerning incarcerated people may become permanent

A federal judge has ruled that the IRS owes stimulus checks to inmates in prison who qualify. If the ruling stands, these people may be entitled to a third stimulus check as well as the first two, with more potential money for dependents.

More mixed-status families could qualify

According to Biden's stimulus plan, more families who are considered "mixed-status" would be eligible for a stimulus check. The second payment broadened the rules for the first check by making it possible for families where one spouse is a US citizen to be eligible for a check. Biden's proposal would work with more scenarios; for example, it would potentially provide stimulus check money to a household of US citizen children with non-citizen parents.

Status for undocumented residents is still unknown

Democrats have proposed that undocumented US residents should be eligible for stimulus relief funds if they pay taxes (through an ITIN number). This provision was part of the Heroes Act that passed the House of Representatives in two forms, but which isn't law. Currently, you need to have a Social Security number to be eligible for a stimulus check.

If a third stimulus check arrives, that would mean this group could potentially get a check for thousands of dollars. For a married couple with two young children who didn't receive the first check, the third round could possibly yield as much as $3,300 for a married couple receiving the full $2,900 benefit and one dependent for $600.

Here's everything else you need to know about stimulus checks today, including what to do if your second check doesn't make it before the Jan. 15 deadline and how to contact the IRS about your missing payment.