UIOSI or Use It or Sell It is a principle stating that when a Market Participant does not nominate its long-term transmission rights, JAO will sell that respective transmission capacity on the relevant daily auction.
Compensation for unused capacity are described in the relevant auction rules available on http://www.jao.eu/resource-center/auction-rules
UIOLI is used for Daily and Intraday rights and where a market participant is not nominating (using) his capacity, his rights would be lost and no compensation would be given to market participant.