If your green card is lost or stolen, you have to file Form I-90, Application to Replace Permanent Resident card with the USCIS.
If you are eligible to apply for Naturalization but lost your green card, you must apply for a replacement for the lost green card before applying for citizenship as you are required to submit your green card while getting naturalized. But, you do not have to wait to receive the new card for filing for naturalization. Once you receive the I-797 Receipt Notice for having filed Form I-90, you can start filing Form N-400, Application for Naturalization.
After you submit the I-90 application package with the appropriate fee and supporting documents (if any) to USCIS, they will send an application receipt notice with a receipt number. As mentioned earlier, you can start the Naturalization process as soon as you receive the Receipt Notice for the Form I-90. You are required to include a copy of the Receipt Notice with the N-400 application.
The application process :
Once you mail your application with the necessary supporting documents and fees, USCIS will start initial processing.
They will send you a Receipt Notice on Form I-797 as an acknowledgement for the application.
After you get the receipt notice from USCIS, you can make an “Info Pass” appointment with your local USCIS office to get an I-551 stamp in your passport.
The I-551 stamp in your passport acts as a temporary proof that you are a permanent resident (green card holder) of the US.
You can use this stamp for all practical purposes that you would be able to use with your original green card (employment, travel, and evidence of status). This stamp is valid for one year.
Expired green card :
Even if your green card expired, you have to get it renewed by filing Form I-90. Always make sure you apply for your new green card well before you travel and bring with you on any trip the temporary documentation that you received from the USCIS. If you are abroad and try to reenter the US with an expired green card, you may face problems causing unnecessary delay during the inspection process at the port-of-entry in the US. So it is always recommended you travel after you file the I-90 application to get a replacement.
Even US employers will not accept an expired Green Card while verifying employment authorization for new hires. In such cases, you can use other documents listed on the Form I-9 (Employment Eligibility Verification Form) such as a social security card and driver’s license, or show temporary evidence of status (such as an I-551 stamp, or even the receipt notice for your Form I-90), Application to Replace Permanent Resident Card.
Another factor is that per the USCIS, if your Permanent Resident Card (Green Card) will expire within six months, you have to renew your green card before filing the application for naturalization (Form N-400). You are required to submit a copy your green card when you apply to become a citizen.