The deadline is funding: points have to be settled before the loan closes and funds. There's no buying the rate down retroactively. The window stays open longer than most people think, though. Even after you've locked, you can still adjust points before closing: pay more to buy the rate down further, or drop the points and take a slightly higher rate with less cash out of pocket. The loan gets re-priced against the rate sheet at your locked terms. Once the loan funds, that door closes, and the only way to change your rate after that is a full refinance with its own closing costs. Our lean, while you're deciding: we lean against paying points as a default. The zero-point quote is the honest baseline, and spending your own cash on a buydown has to survive an honest answer to how long you'll actually keep the loan. The shorter your horizon, or the more likely you are to refinance again, the harder points are to justify, and heavy points are usually money you won't earn back. So make the call during the loan, on purpose. Start from the zero-point price, and if you want to see the loan priced with points alongside it, that's something some people want to see, and we'll run that comparison for you. Decide before you sign, because after funding it's set.