Priority is probably to do the S.M.S. portal first, then the U.K. The U.S. portal doesn't create invoices.

When defining a new set of trade / practitioner prices the tax rate displayed is 0, zero. If this is the tax rate required the "Set" button may not get pressed. When the prices are saved the tax rate is not stored, which means on the phone orders page 20% VAT will be deducted when changing to tax free regions, e.g. "Other"