I O U, a memorandum of debt given by a borrower to a lender, so called from being made in this abbreviated form:
LONDON, 1st January 1889.
I O U Twenty Pounds.
To Mr C. D.
A. B.
It is a convenient document, because it requires no stamp, and yet it is valuable evidence of the existence of the debt, in case an action is afterwards brought. If, however, the I O U contain any promise to pay the debt, then it will amount to a promissory-note, and be void unless it have a stamp. It should be holograph, dated, and addressed to some person or persons, but it does not prove its own date.