Welcome to the QuickBooks community and thanks for choosing QuickBooks Online for your business's bookkeeping! I'm thrilled to have you with us and I can absolutely help you get set up with the meals and entertainment expense sale tax so that you can properly record it in your books.
With more details about what you've done so far and where exactly you're seeing the message you mention, I'm confident we can get to the bottom of this. From what you've described here, however, it sounds like you may not have yet set up the sales tax code for meal expenses and are perhaps trying use the tax liability account specifically, which you cannot do on an expense transaction.
I recommend reviewing the How to set up a sales tax rate for Meals and Entertainment article and following the steps. This sets up a tax code that will track the way you need it to and allow you to easily apply it to your meal and entertainment expenses. That way, you don't have to worry about touching the tax account directly at all. Simply choose the expense account and then assign the tax code to that line for the charge.
If you've already got that set up and are doing as I describe above, it's worth reaching out to our support teams where you can give more details and have someone take a look at what's happening with you. There are a few options to choose from, so pick which works best for you.
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Don't be afraid to get in touch! We're here to help.