• item_name_n
• amount_n
• tax_n
• shipping_n
• shipping2_n
• address1
• address2
• country
• first_name
• last_name
• state
• zip
• item_name
• notify_url
• currency_code
• cart_tax
• tax (the rate of tax)
• cmd (e.g. _cart)
• upload (1)
• custom
• address_override (1)
• weight_cart
• weight_unit
• cancel_return
• cpp_header_image
• cpp_headerback_color
• cpp_headerborder_color
• cs (rgb hex)

https://api-3t.paypal.com/nvp

IPN

• auth_id
• auth_exp
• auth_status (Completed|Pending|Voided)