How can I manually change the tax amounts on an expense? I received a store credit on an expense, the the tax calculation is based on the original amount.

Thanks for posting here, @gcci1963.

Allow me to share some insights about the taxes on expense transactions.

At the moment, the tax calculation for purchases is always based on the tax code you select. If you need to edit the sales tax amount, update the code used or add a custom rate that corresponds to the actual tax amount. Here's how:

1. Go to the Taxes menu, then Sales Tax.
2. Click on the Manage sales tax button.
3. Press Add tax, then click Add under Add a custom tax and agency.
4. Enter the details of the custom rate then click Add to save the changes.

See this link for your sales tax reference: Set up and use sales tax in QuickBooks Online

Please come back here if you have other concerns with QuickBooks Online purchase tax. I'll be right here if you need further assistance. Happy new year from us here in Intuit QuickBooks.