Her contribution to the purchase of the home with her as partial owner has no tax or gift consequences. It is merely her investment in the home. But if you deduct her portion of the mortgage which she has no liability for, the money that she gave towards the mortgage is a gift to you. An amount over $15,000 ($30,000 if given with a spouse) requires reporting with form 709 which is completed and sent by mail separately from her tax return. Because of the large gift/estate tax exemption she won’t owe tax on that gift.
