If you think you made a mistake on the return you've already filed and the IRS accepted, you may need to file an amended return. You'll typically need to amend your tax return if there are changes to your filing status, income, deductions or credits.
If you need to amend your tax return, you can prepare your amended return through Credit Karma Tax, but you won't be able to file an amended tax return electronically. you'll need to print your return and paper file.
If your return was rejected, you do not need to amend your tax return. You can simply edit your return and re-file.