A green card, also known as a Permanent Resident Card (PR Card), can be revoked under certain circumstances. Here are some reasons that may lead to the revocation of a green card:

1. Fraud or misrepresentation: If you obtained your green card through fraud, misrepresentation, or concealment of material facts, it can be revoked.
2. Criminal activity: Committing certain crimes, such as aggravated felonies, drug offenses, or crimes of moral turpitude, can lead to green card revocation.
3. National security: If you pose a threat to national security or public safety, your green card can be revoked.
4. Immigration violations: Violating immigration laws or regulations, such as staying in the US beyond the authorized period or failing to maintain continuous residence, can lead to revocation.
5. Abandonment of residence: If you abandon your US residence or move to another country, your green card can be revoked.
6. Failure to register or report changes: Failing to register with the US Citizenship and Immigration Services (USCIS) or report changes in your address, name, or other relevant information can lead to revocation.
7. Ineligibility at time of approval: If you were ineligible for a green card at the time of approval, but it was granted due to an error or fraud, it can be revoked.
8. Divorce or termination of marriage: If your green card was obtained through marriage and the marriage is terminated or divorce is finalized, your green card can be revoked.
9. Failure to file taxes or pay taxes: Failure to file taxes or pay taxes can lead to green card revocation.
10. Other grounds: Other grounds for revocation include violating the terms of your green card, such as working in a restricted area or engaging in subversive activity.

If your green card is revoked, you may face deportation proceedings and lose your permanent resident status. It's essential to consult with an immigration attorney if you have any concerns or questions about your green card status.