I.O.U., a written acknowledgement of a debt, so called because it commences with those letters, which custom has substituted for the words I owe you, because they have the same sound. It ordinarily runs thus:-
'To Mr. A.B., I.O.U. twenty rupees. C.D January 1st, 2008.'
If in the above form, it requires no stamp, being neither receipt, agreement, not promissory note. If it contains a promise to pay the money, it must be stamped as a promissory note, or as an agreement, if it contains terms of agreement the subject of which is of the value of 5l. It should be addressed to the creditor by name, but that is not essential to its validity. It is evidence of an account stated with the creditor, if named; if he is not named, it is prima facie evidence of an account stated with the person producing it. It is not negotiable.