Has the IRS mailed your stimulus check yet? Track its progress with this free USPS tool

Most of the second stimulus checks have already been delivered to people in the US, through direct deposit -- with some problems -- and mail in the form of a paper check or EIP debit card (more people are getting them this time). And if you're eligible for a second payment of up to $600 per person, but haven't received it in your bank account yet, you may need to pay attention to what's arriving in your mailbox.

There are two easy (and free) ways to track your stimulus check. The first is by using the IRS' stimulus check tracker tool, which can give you information about your payment schedule, how it's arriving, your second stimulus check total and if there's been an error processing your check. Then, if you learn your payment is coming in the mail, you can sign up for a free USPS service that shows you when your letters -- including your second stimulus check -- have been scanned, are in transit and have been delivered to your home.

With a deadline of Friday, Jan. 15 -- just two days away -- the IRS has to finish sending out stimulus payments, as set in the December stimulus bill. If you don't receive your money in the mail shortly after that date, you'll have to file a claim during tax season to get it, and that could affect how quickly your money arrives. (Here's what to know about a third stimulus check, too.) We'll walk you through how you can use the USPS service to monitor your stimulus payment in the mail. This story was recently updated.

USPS Informed Delivery service: How does it work?

Informed Delivery is a free mail-tracking service from the USPS that automatically scans your letters and can alert you with an image each time a letter with your name on it is about to be delivered -- this includes, of course, your second stimulus payment.

When the USPS runs mailed letters through its automated mail sorting equipment, it automatically creates a digital image of the front of all letter-size mail. Anyone who signs up for Informed Delivery can access the information by asking the USPS to notify you when each piece of mail with your name on it is on the way. Note that it can take three days to activate your account.

As part of the program, you'll receive an email each morning, Monday through Saturday, to notify you of any mail being delivered to you. You'll also see a grayscale image of the front of the letter. Informed Delivery has free apps for Android and iPhone that you can use.

Just be aware that signing up means you'll see all your mail scanned by the post office, not just your stimulus check. You can cancel the service at any time.

How to use Informed Delivery to track your second stimulus check

Informed Delivery does have some limitations. For example, it'll work with many residential and personal post office box addresses but not businesses. It also won't work for some residential buildings where the Postal Service hasn't yet identified each unit.

To check whether Informed Delivery is available in your area, head to the Postal Service's Informed Delivery page.

1. Tap Sign Up for Free.

2. Enter your mailing address and confirm it'll work with the service; then accept the terms and conditions and tap Continue.

3. On the next page, choose your username, password and security questions. Then, enter your contact information and tap Continue.

4. On the next page, you'll need to verify your identity. Tap Verify identity online if you want to receive a verification code on your phone or tap Request invitation code by mail if you want the Postal Service to mail you a code. You may also have the option to visit a post office to verify your identity in person.

For more stimulus check details, here's how to calculate an estimate of your total, what we know about a third stimulus check and how some of your rights have changed for the better with a second stimulus check.