I have unknowingly used incorrect VAT codes for some transactions. How do I view all transactions for a certain period of time and see their VAT codes, then change them

Hello, @liz116. It's a joy to welcome you to the Community forum. I'd be delighted to help you track transactions with VAT codes in QuickBooks Online (QBO).

You can run the VAT Detail Report to see all transactions and associated VAT codes for a specific period, then manually change it individually. I'd be glad to show you how:

1. Select the Reports menu, then search VAT Detail Report in the search bar.
2. Change the Report period at the top.
3. Click Run report.
4. Select the VAT code in the report to direct you to its transaction, then modify it there. 
   
   

You may want to personalize the data of your report. Refer to this article: Customise reports in QuickBooks Online.

Click the Reply button below if you need further assistance running reports or any QuickBooks-related concerns. Take care!