Many loan types (auto, personal, etc.) use simple interest. I have a spreadsheet that I use to track my loan balances that B) calculates monthly interest and principal numbers since Quicken does not do simple interest. This should take an annual interest rate and days in a year (or alternatively a daily interest rate), payment amount, first day interest accrues, first payment date, and term of loan, and generates interest, principal, and balance for each month. It's actually a very simple calculation which more often than not is accurate to the penny in my spreadsheet. I'm surprised Quicken does not offer this feature.