I no longer have access to the email they're sending the 6-digit code two for filing

If you're in your tax return you can change your Email address.  

Follow these steps to change your Intuit Account credentials directly in the Intuit Account Manager:

1. Sign in to the Intuit Account Manager. Use your sign-in info for QuickBooks, TurboTax, Credit Karma, or our professional tax products.
2. Select the Sign in & security ICON
3. Choose from User ID, Email address, Password, or Phone section.
4. Make your changes.
5. When you're done, select Save.

Important: Your Intuit Account is connected to all of your Intuit products. Any changes you make apply to all of your Intuit products, including QuickBooks, TurboTax, Credit Karma, and our professional tax products.

Change sign-in information