What does Payment in Lieu refer to?

Übersicht: 

A Payment in Lieu, or Pil, typically refers to a cash debit or credit made to an account in recognition of a stock dividend.  A Pil in the form of a debit will be made when an account is holding a short position in a stock on its ex-dividend date. This debit occurs as the lender of the shares which facilitated the short sale remains entitled to all dividends paid throughout the duration of the loan period.   

Conversely, a Pil in the form of a credit is made when a long stock position in an account has been loaned out on its ex-dividend date.  Account holders should note that shares which are held long and which are the subject of a margin lien may be eligible to be loaned by the broker.  In this situation the credit originates from payment by the borrower of the shares rather than from a dividend by the share issuer.   U.S. taxpayers who are recipients of Pil credits should discuss the tax implications of Pils and non-qualified dividends with their tax adviser.