There are two things you need to know about the second stimulus checks for $600. The first is that the IRS and Treasury are almost done sending out this batch of payments. In fact, about 80% of the total relief money allocated for this round has already been sent, using the two primary ways the IRS has grouped the payments: straight to bank accounts through direct deposit and via the mail as paper checks and EIP debit cards.

The second thing to know is that there’s a Jan. 15 deadline imposed by the text of the stimulus bill, for the checks to stop going out. With 20% of the payments left to go in under seven days, plus a major problem with delivery so far, there’s a chance that your second stimulus check might not make the cutoff — or that you’ll have to claim a make-up payment, called the Recovery Rebate Credit, if you’re missing all or part of the second stimulus check.

After confirming you qualify for a $600 check, the next step is to work out which payment group the IRS has sorted you into. This will give you an idea where to look for your check paying up to $600 per person and what to do if you don’t receive it before the start of the tax season. Read on for details about IRS payment groups below, and here’s where things stand with a third stimulus check for $2,000. This story updates regularly with new information.

Direct deposit payments to your bank account

The IRS has reportedly sent out two-thirds of its $600 stimulus payments through direct deposit, which demonstrates a clear advantage to people who receive an electronic transfer of funds. Direct deposit is a quicker, more efficient mode of delivery than a mailed check, which means the IRS can process many more people faster. (Here’s how to track your second stimulus check online.)

There are two things to know, however. First, some reported problems with checks being sent to the wrong bank account mean that millions of people haven’t been able to receive their stimulus payments through direct deposit after all. And the IRS’ tracking tool won’t let you sign up for or change your direct deposit information this time around.

If the IRS does not already have your banking information, you’ll have no choice but to wait for the mail. If there’s a problem with your payment, you’ll need to wait to file a claim.

Paper checks: Incoming, but two things to know

Paper checks are on their way, at a much faster clip than the first time around — here’s how you can track your stimulus check to your mailbox. There are still two major limitations you need to know. First, 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.

Second, there’s that same Jan. 15 that affects all the payments. So anyone who doesn’t receive their check around the middle of the month will have to claim it this year during tax season. If you’ve recently moved, be sure to tell the IRS and USPS so you can get your stimulus check, and your confirmation letter from the IRS (you’ll need this if you have to file a claim.)

After the cutoff, the timing of your stimulus check delivery then becomes a matter of how soon you submit your taxes for 2020 and how quickly the IRS will be able to process your return. 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.

8 million EIP cards are on their way

EIP debit cards are prepaid Visa cards the Treasury may send you instead of a paper check — the envelope will display the U.S. Department of the Treasury seal, but be careful to not toss your mail without carefully checking first (this free tracking tool can help). The IRS and Treasury have begun sending around 8 million EIP cards, 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 around Jan. 15, you’ll need to claim it as a Recovery Rebate Credit as part of filing your taxes this year.

Social Security beneficiaries: When will you get your check?

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.

For the second check, the IRS will automatically send the money through how you regularly receive your benefits, such as direct deposit, Direct Express card or paper check.

More complex situations are already delaying payments

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.

For the second stimulus payment, people who may fall into this category could include those who have a banking issue with direct deposit, people who moved and still need to tell the IRS and USPS and calculation errors, like people whose estimated payment didn’t match up with what the IRS sent.

It also isn’t clear what would happen if there’s a problem during the Recovery Rebate Credit process and the payment 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. Here are 10 things that could hold up your stimulus check.

What if you’re missing money 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.