Have you lost the USCIS approval notice of your I-130 visa petition or other immigration application? (Or never received it, despite USCIS records showing that it was sent to you?) You may need to use Form I-824.
USCIS often asks people to submit copies of approval notices as part of an immigration process. For example, after USCIS approves a Form I-130 for a family-based immigrant, if that person is in the U.S. and eligible to adjust status here, he or she would need to attach a copy of the I-130 to the adjustment of status packet before mailing it to USCIS.
You might think USCIS could look up the I-130 approval on its own, but the agency is rarely willing to do that. With Form I-824, you can ask to receive your own copy of the approval notice to replace the one that's been lost.
Below are some other situations where a person might need to file Form I-824:
Form I-824 (available from www.uscis.gov) is only three pages long and asks for basic application information including your name, employer, contact information, country of birth, country of citizenship, and identifying numbers. You'll need to attach various documents to help USCIS locate and confirm the original approval, such as copies of the original visa petition or application or a copy of the receipt notice from USCIS (Form I-797). You'll also need to pay the latest fee ($465 as of 2017).
Your completed form must be sent by mail to the USCIS lockbox indicated in the instructions to the form. You can request that you receive an email or text message saying that the form has been received at USCIS by completing Form G-1145 and attaching it to the front page of your application.
The only document USCIS will send after you successfully file Form I-824 is a copy of an approval notice. You can't request any actual replacement cards using this process. For example, if you've lost your green card, you must apply for a replacement by filing and paying the fees for Form I-90. A replacement work permit (employment authorization document) must be requested by refiling Form I-765 (and paying the fee all over again).
Deciding whether you need to file Form I-824 is a good question for an immigration attorney. Don’t spend the money on Form I-824 if you aren't sure you need it. The attorney can also help you prepare the form and monitor progress on your immigration case. In cases where the immigration process isn't going as smoothly as possible, an immigration lawyer is worth the additional cost, because issues with immigration cases are usually much more costly.