Offer your thoughts or opinion on the input financial query or topic using your financial background.

Is there any downside snapping a picture (or scanning a copy) of every check one writes vs. using a duplicate check?
When banks would return the actual physical cheque, at least you had some printing / writing from the other bank on it, as some type of not-easily-Photoshopped proof. Now many (most?) banks don't return the actual cheques anyway, just an image of it - sometimes a low quality shrunken B&W photocopy-like image too.  You'd have to check with a lawyer or court in your area, but I suspect any photocopy or image, as well as a written or carbon-copy duplicate, would not be good enough proof for a law court, since they could all be easily re-written or Photoshopped. So I don't think there's a real upside anyway. Only an official bank statement saying that the name/people written actually cashed the cheque might be "good evidence" (I'm having doubts that the bank's own low quality "image" would even qualify, unless it's verified as coming directly from the bank somehow). I'd agree with Nate (+1) that a big downside could be identity theft, either online or alongside phone loss/theft.