Can I give one product a different tax rate, or make it tax-free?

Not at the moment. WCart has no tax class or tax-exempt option on products. The product form's pricing section notes that tax handling follows your store tax settings.

Tax is worked out for the whole order: the rates in Settings → Store Settings → Manage Tax are matched to the customer's address, and the matching rate applies to every product in the cart.

What this means in practice:

• Set your rates to the one that covers most of your products.
• A product that should carry a lower rate, or none, will still be charged that rate at checkout and shown with it on the invoice.

If you sell a real mix of rates or exempt goods, check with your accountant before going live, and post here if per-product tax rates matter for your business.