There’s many do’s and don’ts when it comes to writing a check, namely correctly filling it and using the correct writing-device. The problem with using Sharpies or Markers on checks is that they can bleed through the check, and thus many banks will not accept them simply based on principle even if the check is perfectly legible. So while sometimes all you can find is a Sharpie or Marker, don’t waste a check writing it like that — find yourself a proper pen to write that check out with first.
Endorsing a Check in Sharpie or Marker has the same issue as writing with sharpies/markers anywhere — they have the potential to bleed through the check making it invalid, and thus many banks will refuse to deposit such checks even if no bleeding-through occurred. As a result we’d recommend not using a Sharpie OR or a Marker when endorsing a check — find yourself a good blue/black ink pink to do it, if you don’t have one any bank or western-union type place will have one you can use no-problem, even if you aren’t doing business with them but rather just using the pen for a moment.
As we covered above, no banks will not accept checks written in Sharpie or Marker in most cases due to the fact that they can bleed through the check and thus many banks have a policy of refusing checks written with markers and invalidating them. The same applies with ATM’s or mobile apps that accept check deposits — some may accept them, however generally the AI that reads them will refuse the check as the written lines are too thick when using sharpie/marker, and potential bleed-through makes the AI believe the Check is not focused or valid.
The best thing to use to write and endorse checks are simple blue or black ink pens; they’re what banks prefer and virtually never will bleed through or confuse the ai check validation mechanisms in ATM’s or mobile-deposit apps.
Really any color of pen works for most banks and mobile deposit options, however sticking to black/blue ink is definitely the preferred choice and what we’d recommend.