My accountant wants every counter receipt to be a proper tax invoice with my TRN on it. Can the POS do that?

Yes. Save your tax number under Settings → Ordering rules, in the Invoices section, and every receipt the POS prints becomes a tax invoice with the VAT line and your TRN on it. Without a tax number saved it prints as a plain receipt and claims no tax. Any past sale can be found with Find a sale on the device and printed again, and the Arabic copy is one tap away if the tax authority asks. That is what makes the POS usable as your restaurant billing software rather than a second system beside it. The POS and the counter tab in the docs covers receipts and the tax lines.