Does your $1045 include escrows, or is that just principal and interest? IF it’s just P&I, and you do the lump sum to take the balance to $49,000, then continue to pay $1045, you’ll pay the loan off in just over 4 years. You should note that on that small of loan size, that far into the repayment schedule, the interest you pay is quite minimal. I understand the appeal of having the mortgage paid off, but would advise that you make sure you have ample savings, retirement accounts funded, any other debt paid off (since it would likely be at a higher rate) before putting those funds towards the mortgage. Congrats either way, nice to be near the end of your payments!