Returning deposit early? Payment receipts...

I am a landord in Illinois renting out a single family 3 bdr home. There is a lease with my tenant outlining all the standard lease provisions including the security deposit which is a half months rent. When the tenant paid first months rent and sec deposit I signed a receipt for each. For the deposit receipt, I unknowingly signed the receipt without looking at the dates which the tenant filled out as "deposit for May 3rd to Feb 28th" (instead of May the following year) . There was no discussion of returning the deposit a couple months early as the standard practice is returning the deposit at the conclusion of the lease. The tenant is now (several months later in January) requesting that I return the deposit on Feb 28th which I have initially refused. She says that "well, you signed the receipt". I feel that though I signed the receipt the tenant was deceptive in not discussing it with me as an agreement different than what is stated in the lease regarding the deposit. Can the tenant hold me to returning the deposit on Feb 28th because of the signed receipt with a different date? - Is this your question? Add additional information