The IRS is stating that they have already accepted and processed a tax return for this year with that Social Security Number.
How to fix this rejection depends on what caused the rejection. There are several possible scenarios for receiving this code:
Check that the Social Security Number or ITIN was entered correctly
To make certain that you entered your social security number correctly, log in to your account and go to the basic information section. Then go into the personal information section and verify that you have entered in all the social security numbers correctly into the system.
If you did incorrectly input your social security number, you will need to correct it and then re-submit your return through the e-file process.
What if I was only filing a state return?
Sometimes taxpayers wish to file their State Only return after they filed their Federal return using another e-file provider. However, they mistakenly resubmit their Federal return with their state return although the IRS has already accepted the Federal return, causing the duplicate submission rejection code.