So very late last year I sold my Nikon D90 to a nice lady not too far from where I live, we met up and she bought it on the spot. Now she's doing her taxes and wants a 'receipt' with the date of sale, amount and my signature. She's a professional photographer and got this as a backup camera. I'm having a hard time grasping this, is this normal? She needs me to send it out today. This is the lady I'm second shooting with for a couple weddings this summer. She's really nice and everything, but for some reason I'm not comfortable with it. I'm not a retailer, it was a private sale. Thoughts?