Keeping your personal purchases separate from your business purchases is essential.  Bank statements with a mixture of purchase types are difficult and time consuming for your bookkeeper to sort through.  Remember, time is money.  The more complicated your bank statements, the longer it takes to reconcile resulting in higher bookkeeping costs for you.  In addition, this practice leaves your personal life exposed which neither you nor your bookkeeper may be comfortable with.  And though sole proprietorships are not required to keep separate records, it is a good habit to get into.