Even though i have entered the tax codes in the chart of accounts, i still have to enter them when i'm posting

Hello kristalynnemille,

Thanks for being a long-time member of the QuickBooks Community! Ensuring that your sales tax codes are correctly added to your transactions is an important part of the bookkeeping process. Managing sales tax and the codes you need is a breeze with QuickBooks Online, so I'm happy to have you on board. Let's go over this.

When you've entered a default tax code for the accounts in the Chart of Accounts, it's meant to automatically populate when you create a transaction with that category selected, as you know. It's critical that you use the Category details section of the transaction, and select the correct account from the Category dropdown column. If you're doing this, the Sales Tax code that you've saved should pre-fill in the corresponding column. 

Since it sounds like you're doing everything correctly, I want to suggest that you try some browser and internet troubleshooting. Sometimes the images and files that are saved in your browser's or app's cache can cause issues with the way QuickBooks functions. The steps below should help to determine if the issue is browser-related or if it's something our team of engineers might want to look into.

• Clear your browser cache if you're using a browser
• Clear the app cache if you're using the QuickBooks Online app for Windows or Mac
• Try a browser if you're using the app
• Try a private browser window
• Try another browser type
• Make sure you're using a supported browser and system
• Reset your Internet or try on another computer or device

If these troubleshooting steps don't quite hit the mark and you still have to manually add codes to your transactions, please reach out to us outside of the Community. That way we can collect some sensitive account details in order to create a case and report this issue to the appropriate teams. When there's a fix, you'll get notified via email. Here's how you can reach out:

Phone: Call us at 1-855-253-1536 from Monday to Friday between the hours of 9 AM and 8 PM EST.
Schedule a Callback or start a Chat: click (?)Help in the upper right > type and enter "Contact support" into the QB Assistant > click Contact Us > explain your situation > click Let's Talk > choose Get a callback or Start a Chat. 
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Don't be a stranger. If you have more QuickBooks questions, you're always welcome to reach out here. Have a great day!