I always pay extra principal every month and the "what if" tool allows me to see my estimated early payoff date. But now I received a bonus and want to estimate the impact of paying a one-time lump sum amount AND continue to pay the extra principal every month. All I can do right now is pay the lump sum, wait for it to be processed, update Quicken, and THEN see the new payoff date with the extra principal each month. It's a bit annoying because my lump sum amount is flexible and it would be great to know what the best lump sum amount is based on payoff date.