A check holds all of the information needed to steal your identity: name, address, bank account, routing number. If written with a ball-point pen, information can easily be removed by a process called check washing, a common form of identity theft. It is the process of taking a check or document that has already been filled out, removing the ink with a regular household chemical, then re-writing in a new dollar amount and recipient. If you are careless, your personal check could contribute to the 1.2 million fraudulent checks written every day. That's more than 13 per second.
When writing checks and filling out important documents, use a gel pen, like the Uni-Ball 207, so thieves can't remove the ink and change the information. These pens trap the ink within the fibers of the paper, making it essentially impossible for check washing to occur.