protected override async Task <object> OnPerform()
        {
            var response = await _restClient.VerifyTaxExempt(
                _cacheManager.SaleNumber, _cacheManager.TillNumberForSale,
                _cacheManager.RegisterNumber);

            var data = await response.Content.ReadAsStringAsync();

            switch (response.StatusCode)
            {
            case HttpStatusCode.OK:
                var taxExemptVerification = new DeSerializer().MapTaxExemptVerification(data);
                return(new Mapper().MapTaxExemptVerification(taxExemptVerification));

            default:
                return(await HandleExceptions(response));
            }
        }