If my social security number is off by one number and I already submitted my taxes, will it effect my return even if its the same employer as last year?

If your SSN is wrong, even by one digit, your return should be rejected. So you can make the correction and resubmit.

If your social security number were entered in the My Info section, then your return will likely be rejected.  If the tax return is rejected, then you have the chance to return to the program to make corrections, then resubmit the return by efile. 

If your return was truly accepted by IRS with the wrong social security number, I would suggest you contact IRS for the corrections. 

To contact IRS, you can either call 800-829-1040

or visit your local IRSOffice

It's important that you check the status of your return daily so that if the return is rejected (as seems likely), you can fix it and refile it as quickly as possible.

If your return is rejected, see Fix Reject