After working with pre-retirees for years, I see the same three mistakes over and over. They're not about picking the wrong stocks or retiring too early. They're about arithmetic.

Mistake #1: Assuming Social Security replaces your paycheck timing.

Your paycheck hits every two weeks like clockwork. Social Security pays once a month — and usually not on the 1st. If your mortgage autopays on the 3rd and your Social Security hits on the 12th, you've got a 9-day cash gap in month one. Multiply that by three or four fixed expenses and you're overdrafting in retirement. Not because you're broke — because you didn't map the timing.

Mistake #2: Ignoring the tax bite on early withdrawals.

Most people know they'll owe taxes on 401(k) withdrawals. What they don't plan for is when those taxes actually hit. If you withdraw in January and don't adjust your quarterly estimated payments, you could owe a penalty by April. The first-year withdrawal plan needs a tax withholding line item for every single month — not an annual estimate divided by 12.

Mistake #3: Running one scenario and calling it a plan.

A baseline projection is not a retirement plan. It's a best-case guess. What happens if inflation runs 6% instead of 3%? What if the market drops 20% in your first year? Those aren't hypotheticals — they've both happened in the last five years. You need at least three scenarios: baseline, inflation shock, and market drop. Then you need a simple system to decide which actions to take under each one.

I built a full framework around these three problems — mapping income sources, stress-testing three scenarios, and using a traffic-light decision system (green/yellow/red) to know exactly what to do.

If you're 55–67 and within a few years of retirement, the time to figure this out is now — not the month your last paycheck hits.