QuickBooks decided to end OAuth 1.0 support for all their apps by the end of January 2020. This was done for security reasons and you can read more information about the OAuth 1.0 to OAuth 2.0 migration efforts on the QuickBooks API documentation pages.

STEP 1 - Developer Portal

Navigate to https://developer.intuit.com/ and click on Sign In at the top right-hand side. You will see the login screen below.

STEP 2 - Login

Use the same login and password as you would when accessing your LIVE QuickBooks account.

STEP 3 - Create a new app

After a successful authentication click on My Apps at the top right and you will be redirected to the QuickBooks app dashboard. It should look similar to this:

STEP 4 - Create a new app

Click the blue-button at the top of the page with the following label: + Create an app

Click on QuickBooks Online and Payments box and fill out a form on the next image.

The app name can be anything, but we recommend you use a descriptive name (eg. Integration with mystore.com)

The scope should be set to Accounting.

Click on Create app button.

STEP 5 - App configuration

Click on Production Settings

We don't recommend using ALL as it will increase the security risk for this integration app.

Click Save.

STEP 6 - App assessment questionnaire

On each page click save to ensure the answers are saved and if you can`t finish the questionnaire by some reasons right now the next time you enter answers will be already populated.

Click Submit.

STEP 7 - Keys and OAuth

Click Save.

FINAL STEP

Go to Configuration: Connecting to QuickBooks to connect your app to Magento.