我们使用 Express Checkout 并希望根据结账时在 PayPal 上选择的送货地址计算税款。我们可以增加订单总额来计税，但税额始终记录为零。这是我们的流程：
我们SetExpressCheckout将PAYMENTREQUEST_0_AMT订单总额PAYMENTREQUEST_0_TAXAMT设为零（或省略），以及MAXAMT订单总额 + 最大可能税额。
在回调时，我们运行GetExpressCheckoutDetails以查找送货地址。
如果有税，我们会DoExpressCheckoutPayment以PAYMENTREQUEST_0_AMT（订单总额 + 税）和PAYMENTREQUEST_0_TAXAMT税的形式运行L_PAYMENTREQUEST_0_TAXAMT0。
总订单按金额（订单总额 + 税金）处理，但PAYMENTINFO_0_TAXAMT返回的始终为零。
是否需要传递其他字段才能正确应用税款？
设置：
METHOD: "SetExpressCheckout"
PAYMENTREQUEST_0_PAYMENTACTION: "SALE"
PAYMENTREQUEST_0_AMT: 1.00
PAYMENTREQUEST_0_ITEMAMT: 1.00
PAYMENTREQUEST_0_SHIPPINGAMT: 0
MAXAMT: 1.1
L_PAYMENTREQUEST_0_QTY0: 1
L_PAYMENTREQUEST_0_AMT0: 1.0
捕获：
METHOD: "DoExpressCheckoutPayment"
PAYMENTREQUEST_0_PAYMENTACTION: "SALE"
PAYMENTREQUEST_0_AMT: 1.1
PAYMENTREQUEST_0_ITEMAMT: 1.1
PAYMENTREQUEST_0_TAXAMT: 0.1
PAYMENTREQUEST_0_SHIPPINGAMT: 0
L_PAYMENTREQUEST_0_TAXAMT0: 0.1
L_PAYMENTREQUEST_0_AMT0: 1.0
结果：
ACK: "Success"
VERSION: "95"
BUILD: "7161310"
PAYMENTINFO_0_TRANSACTIONTYPE: "cart"
PAYMENTINFO_0_PAYMENTTYPE: "instant"
PAYMENTINFO_0_AMT: "1.10"
PAYMENTINFO_0_FEEAMT: "0.33"
PAYMENTINFO_0_TAXAMT: "0.00"
PAYMENTINFO_0_PAYMENTSTATUS: "Completed"