code: public final TaxDestination revealTaxRules(final Map<String, Object> pReqVars,
      final IInvoice pInv, final AccSettings pAs,
        final Boolean pIsExtrTx) throws Exception {
      return this.utlInvBase.revealTaxRules(pReqVars, pInv, pAs, pIsExtrTx);
    }
docs: <p>Reveal shared tax rules for invoice..</p>
  @param pReqVars request scoped vars
  @param pInv invoice
  @param pAs Accounting Settings
  @param pIsExtrTx if extract taxes
  @return tax rules, NULL if not taxable
  @throws Exception - an exception.