<prompt> Human: My wife and I both 40 yo are trying to decide whether we should pay off our mortgage or invest a lump sum of cash were receiving. We have two children under the age of 4 and have a combined pretax income of 200k. No car payments or student loan payments. My wife and I are both currently maxing out our 401k allocations. Between IRAs, 401k and brokerage investments, we have 500k invested. We have a 6 month emergency fund saved and contribute to 529 plans for each of our children.In a month we will be receiving a lump sum of 154,000. We currently have 214k initially it was 260k it left on our 20 year mortgage at 3.5.Any thoughts on whether to pour that 154k onto the mortgage or whether to invest it would be greatly appreciated?  <response>: Being debt free might not be mathematically optimal in this situation, but living without debt is a goal in itself, and I definitely understand why you would do it. You could always split the difference and do it 5050 if you arent sure. 