By the end of the work week, the IRS and US Treasury must stop sending second stimulus checks. Why? It’s actually part of the legal language written into December’s stimulus bill. But surely there will be checks for $600 or far greater that for one reason or another don’t get calculated by the IRS or issued by the Treasury by the Jan. 15 deadline for stimulus checks.

Or maybe the checks will run into an issue like this one and have to be returned to the IRS. So if you qualify for a stimulus check and didn’t get your payment, there are some things you might want to understand. For example why does this cutoff exist and how that sets your checks behind if you don’t get your stimulus money by then.

We’ll also explain what you need to know about receiving stimulus money through direct deposit, paper checks and EIP cards. Also, we’ll go over the second stimulus check payment timeline from here and how a delay could affect you. Here’s how to track your stimulus check status, follow your payment arrives to your mailbox and what we know about a third stimulus check for up to $2,000 per person. This story recently updated.

Why is there a Jan. 15 stimulus check deadline?

The writers of the legislation didn’t explain why they chose a Jan. 15 cutoff date to send stimulus payments, but that only gave the IRS and Treasury a total of 17 days to send out over 100 million stimulus checks. That’s two days less than the time it took for the IRS to begin sending the first stimulus check after that bill passes in March (it was 19 days, for the record.)

Tax season, which heavily involves both the IRS and Treasury, typically begins in mid-to-late January and continues through April 15, and may be a factor in the Jan. 15 deadline.

Read more: Stimulus check formula decoded: This is why you got what you did.

What happens to the stimulus check delivery timeline if your payment doesn’t make the cutoff?

If you don’t receive your full second stimulus check money shortly after Jan. 15, it doesn’t mean you’re out of luck claiming your rightful stimulus money. But it does mean your payment could be delayed by months.

That’s because you’ll need to take the extra step of claiming all or part of the missing amount when you file your federal tax returns this year as a Recovery Rebate Credit. You’ll also be able to claim any money the IRS still owes you from the first round of checks as part of the credit.

Some people who received their stimulus payment through direct deposit have run into problems. If you experience any issue or hold up with any payment method — again that’s EIP cards, paper checks and direct deposit — it means you’ll have to take the extra step of filing a claim.

It isn’t entirely clear how quickly the IRS would process the Recovery Rebate Credit, but the process of making a second stimulus check dependent on the 2020 tax return will almost certainly delay the payment for many, especially since circumstances mean some people will file taxes as early as January and others as late as April 15, or even later if they need to request an extension.

Read more: Just do us a favor and avoid these stimulus scams, OK?

Two smart ways to track your $600 stimulus payment

The IRS has reopened its online Get My Payment tracking tool with information on the second round of payments. With the free-to-use portal, those who qualify for a check can see the status of both the first and second payments. The website is available in English and Spanish. You can also use a free tool from the USPS to follow your check’s movements to your mailbox.

Direct deposit payments may still happen through Friday

The IRS sent the first direct deposit payments on Dec. 29, and as far as we can tell, the IRS and Treasury are continuing to processing bank account transfers. People who have run into issues with direct deposit that aren’t resolved by Friday need to address them during tax season 2020.

While most eligible individuals don’t need to do anything to receive the second payment — provided the IRS already has your banking or mailing information on file — you also can’t sign up for direct deposit or do much to correct your banking information on file if you closed an account. If the IRS can’t deliver your payment, you’ll need to claim it on your taxes.

Paper checks and EIP cards: Why they might not all make the deadline

If the IRS doesn’t have your current direct deposit information on file, it will send the payment as a check or EIP debit card in the mail. Again, it isn’t clear if the IRS has time to deliver the tens of millions of payments before Jan. 15 in such a short window of time. The IRS was able to process between 5 and 7 million a week with the first stimulus check, according to a government report from June.

Here’s how you can track your status with the IRS and track your second stimulus check to your mailbox, for free, to set your expectations and to help prevent you from accidentally throwing it away. If you’ve moved recently, tell the IRS and USPS.

Speaking of EIP cards, you might get one this time

The IRS is making 8 million payments through an Economic Impact Payment prepaid debit card, the agency told CNET in an email. That’s twice the number that was sent for the first stimulus check. Even if you got paid with a paper check the first time around, many more people might receive a debit card this time. On the flip side, some people who received a debit card last time may receive a paper check.

The IRS warns that those who are eligible but don’t receive a direct deposit should watch their mail for a check or EIP debit card. The debit cards will arrive in a white envelope that displays the US Department of the Treasury seal, the IRS said.

What’s the longest you might wait for your new stimulus check?

People who will receive their second stimulus check in the mail — either as a paper check or a prepaid debit card — should look for a payment anytime from now through Jan. 15. According to the Treasury, 22% of the payments as of last summer were made as paper checks and another 3% as prepaid debit cards.

After Jan. 15, you will have to claim any money the IRS owes you with your tax filing in 2021. That could further delay your stimulus check, since the timing would depend on:

• When you file your 2020 taxes — the deadline could be April 15, unless you file for an extension.
• How long it takes the IRS to process your tax return, which may also include your second stimulus check.
• If there are any complications that arise in your specific scenario that could further delay your check.

We’ll keep our eye on the situation, which is constantly evolving. Here’s how to calculate your estimated total now for a $600 per person maximum.