Section 2--310. Open Time for Payment or Running of Credit; Authority to Ship Under Reservation

Unless otherwise agreed
    (a)  payment  is  due  at  the time and place at which the buyer is to
  receive the goods even though the place of  shipment  is  the  place  of
  delivery; and
    (b)  if  the  seller  is authorized to send the goods he may ship them
  under reservation, and may tender the documents of title, but the  buyer
  may  inspect  the goods after their arrival before payment is due unless
  such inspection is inconsistent with the terms of the contract  (Section   2--513); and
    (c)  if  delivery  is authorized and made by way of documents of title
  otherwise than by subsection (b) then payment is due  at  the  time  and
  place at which the buyer is to receive the documents regardless of where
  the goods are to be received; and
    (d)  where  the  seller is required or authorized to ship the goods on
  credit the credit period runs from the time of shipment but  post-dating
  the  invoice  or  delaying  its  dispatch will correspondingly delay the
  starting of the credit period.