I always get duplicate checks. I write hard enough that I can still read the carbon paper, and since I write down the account number of whatever bill I am paying it is nice to be able to reference the account number when I write out my checks. Usually I write all my checks out when I get paid and just stick them in the bill envelope when I get home. But since I am meticulous with my checkbook there is never any worry that I will forget to write down a check. If I ever have problems balancing my checkbook (which I do every two weeks when I get paid) it is because I wrote something down that I actually paid cash for.