Hi there, @Kymley.

Let me help check why you have to manually check the Tax field on the billable expense added to your invoice. It should be able to automatically apply the sales tax rate since you've already set up the customer as taxable and your Charge Sales Tax is activated as well.

Can we look into your billable expense transaction again to verify if there's a check mark on the Tax field? Please see attached screenshot for your reference.

Once you apply this bill to an invoice, it should automatically check the Tax box on each line item.

Keep me updated how it goes. We'll continue to isolate this further if the issue persists. I'll be here to help if you have additional questions about your billable expense.