To automatically create a business contact each time you create a check, deposit, sale or purchase, click the Banking, Sales or Purchases tab in the Preferences window, then mark the box labeled, "Make a Contact Log Entry for Every...."
Over time, business contact information can cause your company file to grow considerably in size. If you choose to create business contacts automatically, we recommend that you periodically purge old contacts that you no longer need. (Purging information that's no longer needed)