Is tax worked out from the customer's delivery address?

Yes. At checkout, Wcart matches your tax rates against the country, state, city and pincode the customer enters for delivery. The total updates as they fill in the address.

Until an address is entered, only your store-wide rate (all levels *All ()**) can apply. The final tax is set by the address on the order.

To check your setup, start a checkout with an address in each state you tax and look at the tax lines in the order summary. Rates are managed under Settings → Store Settings → Manage Tax.