You continue to record household purchases in the same old paper pad that comes with the checks. Yes, it is free and you can slide it into your pocket or pocketbook if necessary. Other than reminding you that you spent money it has no functionality.
It cannot, to name a few things: report to you that current balance in your checking account, sort expenditures according to your budget categories or list your deductible expenditures for tax preparation. Do yourself a favor and download a checkbook balancer that will provide all of the above as well as a few other features.