The IRS and US Treasury have less than two weeks to process tens of millions of second stimulus check payments before reaching a Jan. 15 cutoff to complete sending payments. Yes, this is actually written into the $900 stimulus bill. The payments will continue for the next 12 days through direct deposit, physical checks and EIP cards, but not everyone who qualifies for more stimulus money will get their check right away. (Here’s how to calculate your stimulus check total.)

So far the IRS has acted quickly, but the tight deadline presents some timing limitations. Other issues could also potentially hold up your second stimulus check. Where you slot into the payment schedule can give you an idea if you’ll be one of the first in line to get a second stimulus check for up to $600 per person, or near the end. (Here’s why some people may not get another check at all.)

We’ll explain more below. By the way, the last-minute push to replace the $600 checks with $2,000 maximum died in the Senate Jan. 1, but President-elect Joe Biden has already committed to a third stimulus check in 2021. Read on for more information about which IRS payment group you may be in. This story was recently updated.

First group: People with direct deposit already set up

People who have their direct deposit information on file with the IRS are in the first group to receive a stimulus check. An electronic transfer of funds is faster and more efficient than mailing a check, which means the IRS can process many more people faster. Some have already received their money through direct deposit, beginning on Dec 29.

As of Jan. 2, the IRS has not made it possible to sign up for direct deposit if you didn’t have it already, or to track your payment, but we expect to see the online tool activate in the coming week. Here are ways you can help speed up delivery of your next check, including what we know now about signing up for direct deposit.

For Social Security beneficiaries, two main scenarios

With the first stimulus payment, many people who receive Social Security disbursements who also had direct deposit information on file with the federal government received checks in the first week, though not always the first day.

The IRS had a separate informational section for people who receive SSDI and SSI. Normally, people in these groups receive their federal benefits through a Direct Express card, though people in this group received their stimulus payment through a non-Direct Express bank or a paper check.

Paper checks are already on their way, but…

The IRS began sending the first paper checks in the mail on Wednesday, Dec. 30 (here’s how you can track your stimulus check to your mailbox). That’s much faster than the first time around, but there are still two major limitations you need to know.

The US Treasury can process between 5 million and 7 million paper stimulus checks a week in addition to checks for other federal programs, according to a Government Accountability Office report from June, which means some people will have to wait.

Then there’s this catch. Language in the stimulus bill institutes a cutoff of Jan. 15 for the IRS to send out payments. So anyone who doesn’t receive theirs by Jan. 15 will have to claim it in early 2021 during tax season. That gives people who sign up for direct deposit a distinct advantage.

The timing then becomes a matter of how soon you submit your taxes for 2020 and how quickly the IRS would be able to process your return. Those two scenarios are influenced by a variety of factors. For example, people who file their returns in February would likely receive their stimulus check money — in the form of a Recovery Rebate Credit — months before people who wait until the April 15 deadline or file an extension.

The first batch of EIP cards is arriving much faster this time around

EIP debit cards are prepaid Visa cards the IRS may send you instead of a paper check — the envelope will look unmarked, so be careful not to toss out your mail without carefully checking first (this free tracking tool can help). The IRS has said it will start sending EIP cards this week, a change from the one-month delay in sending this type of payment the first time. The same rules apply as paper checks. If you don’t get yours by Jan. 15, you’ll need to file a Recovery Rebate Credit between Jan. 16 and April 15 as part of tax season.

People who have more complex situations will likely wait the longest

For the first check, this category includes people who received a check after June, still haven’t received their full stimulus payment or who didn’t know they needed to complete an extra step. It isn’t clear what would happen if there was a problem during the process and the Recovery Rebate Credit was further delayed. It’s likely the IRS would set a different, later deadline to address clerical errors, like missing stimulus money, and other scenarios.

What to do if you still haven’t received the full amount from either stimulus check

It isn’t always clear how much money the IRS might owe you in the event of an error. We suggest starting with our second stimulus check calculator or the calculator for the first stimulus check and this introduction to how the IRS tabulates your total sum. If the numbers seem lower than they should be, you might want to investigate further.

See if any of these situations could apply to you: Are you missing $500 allotted for your child dependents, or do you pay or receive child support? Are you a tax nonfiler who may be owed a stimulus check (including older adults and people who receive SSI or SSDI)?

If you’re a US citizen abroad or live in a US territory and didn’t receive a check as expected, you may also need to read up on the rules. And a court ruling has made it possible for millions of people who are incarcerated to get a check, even after the IRS changed its interpretation to exclude this group.