I used to work at a bank and once during our monthly meeting a couple of investigators from the DA's office came to talk to us about different scams; identity theft, etc. They told us to NEVER use a regular ball point pen to write a check as the ink could be "washed" and the check could be re-used. They said to always use a gel ink pen, that the gel ink wouldn't wash off. They demonstrated by putting some regular nail polish remover in a small bowl and dipping the check and using a cotton ball to wipe until all the ink was off. Some crooks are very meticulous and leave the signature intact; but that's not really necessary since banks clear clecks electronically and only spot check signatures. If there is such a problem, though, your bank will refund the monies lost after filing a police report.