The Finance Charge preferences are a collection of options that have to do with the interest rates and charges that come with customers who are late on their payments. Because this is a company-wide setting, there are no options in the My Preferences tab, only the Company Preferences tab.

• Annual Interest Rate
  • This is where you enter the interest rate for finance charges. QuickBooks uses a percentage format, so if enter 15.4 into this box, QuickBooks will read this as 15.4%
• Minimum Charge
  • If you want QuickBooks to apply a flat finance charge to all overdue accounts, enter that number in this option.
• Grace Period
  • This is simply how many days before a payment is considered late. Notice that the number is in days, so if you have a grace period that spans 2 months, you would need to enter 60 into this field.
• Finance Charge Account
  • From this drop-down box, you can choose the account that you use to enter in money from charges.

You can read here part 2 of this article.