“ A friend told me yesterday that since I filed head of household, I should have claimed a deduction for the taxes on my mother's house even though it's her house not mine. Is this true?”-->No, Idon’t think so; to deduct your mother’s real estate taxes, the taxes must be imposed on you taking the deduction. Real estate taxes would be imposed on the owner of the property, your mother, I guess as she is an owner of the home. The Tax Court has allowed beneficial owners to also claim the deduction. Assume that your area cosigner, even the co-signer would not be a legal owner and the status of beneficial owner is a very difficult one to establish.Hence the co-signer cannot deduct the real estate taxes.