a1c47b6d_ation__NVP____PayPal_Developer__Field
[Description] (Conditional) How you want to obtain payment. When implementing parallel payments, this field is required and must be set to Order. When implementing digital goods, this field is required and must be set to Sale. You can specify up to 10 payments, where n is a digit between 0 and 9, inclusive; except for digital goods, which supports single payments only. If the transaction does not include a one-time purchase, this field is ignored. It is one of the following values: Sale – This is a final sale for which you are requesting payment (default). Authorization – This payment is a basic authorization subject to settlement with PayPal Authorization and Capture. Order – This payment is an order authorization subject to settlement with PayPal Authorization and Capture. Note: You cannot set this field to Sale in SetExpressCheckout request and then change the value to Authorization or Order in the request. If you set the field to Authorization or Order in SetExpressCheckout, you may set the field to Sale. Character length and limitations: Up to 13 single-byte alphabetic characters. [Field] 
PAYMENTREQUEST_n_PAYMENTACTION
DoExpressCheckoutPayment API Operation (NVP) - PayPal Developer
Field