Lottery tickets are bearer instruments, which means that the Lottery must pay the holder of a winning ticket presented for payment. Signing the back of the ticket is the single most important thing one can do to help protect themselves from theft and demonstrate ownership of the ticket. Any alteration to a winning ticket worth more than $600 is cause for an immediate security investigation. Once a winning ticket has been paid, however, it is much more difficult to determine whether another individual was the rightful owner. By law, the Lottery can pay a winning ticket only once.