If you have received an IRS reject code R0000-198 when filing your tax return, it means that the IRS has already received a tax return with the same Social Security number (SSN) or Individual Taxpayer Identification Number (ITIN). Here are some steps you can take to resolve the issue:

1. Double-check the SSN or ITIN you entered on your tax return to ensure that it is correct.

2. Verify that you have not already filed a tax return for the current tax year using the same SSN or ITIN. You can check the status of your tax return by using the "Where's My Refund?" tool on the IRS website.

3. If you find that you have already filed a tax return, you may need to amend your tax return or contact the IRS for further assistance.

4. If you have not already filed a tax return and believe that the reject code was issued in error, you can contact the IRS e-file Help Desk at 1-866-255-0654 for further assistance.

It is important to resolve any IRS reject codes as soon as possible to avoid delays in receiving any refunds or other benefits you may be entitled to.