Common retirement planning mistakes
Last updated August 2026
Short answer
The investment questions get the attention and the planning questions decide the outcome, which is why so much retirement advice is aimed at the wrong half of the problem.
Planning from a number rather than a budget
Round targets are memorable and say nothing about what a year of your life costs.
The useful method starts with annual spending, subtracts Social Security and any pension, and sizes the portfolio against what remains.
Spending is also not flat: higher in the early active years, lower in the middle, and potentially much higher late if care is needed.
Underestimating healthcare
Medicare begins at 65, so anyone retiring earlier needs coverage for the gap through the marketplace, COBRA or a spouse.
Marketplace premium subsidies depend on income, which the choice of withdrawal source partly controls.
After 65, Medicare is not free either: Part B premiums, Part D, supplemental coverage and out-of-pocket costs all belong in the budget.
Claiming Social Security by default
Claiming at 62 reduces the benefit permanently, and delaying to 70 increases it, inflation-adjusted, for life.
For a married couple the higher earner's decision sets the survivor benefit, so delaying that one is worth more than the single-life arithmetic suggests.
The mistake is not claiming early. It is claiming early without ever having compared the alternatives.
Try it in Walnut
Walnut connects to your brokerage and reads what you hold across accounts, which is where a withdrawal plan has to start.
One tax treatment for everything
A retirement funded entirely from traditional balances means every dollar of income is ordinary income.
That drives the taxation of Social Security benefits, Medicare premium surcharges and marketplace subsidies all in the same unhelpful direction.
Holding traditional, Roth and taxable money together is what makes it possible to choose which bucket a withdrawal comes from.
Getting the risk shape wrong
Too much equity leaves you exposed to a poor first decade, which withdrawals turn into permanent damage.
Too little leaves a 30-year retirement exposed to inflation, which erodes purchasing power quietly and continuously.
Holding several years of spending outside equities addresses the first without abandoning growth on the rest.
Ignoring the last chapter
Required distributions from 73 force taxable income out of traditional balances whether or not you need it.
Long-term care is largely outside Medicare and can be the largest expense of a retirement.
Both are foreseeable, and both are considerably cheaper to plan for at 60 than to discover at 80.
The order these are worth fixing in
Build the spending estimate first, because everything downstream depends on it and nothing else can be sized without it.
Then price healthcare for the years before Medicare, which is the largest uncertainty for anyone retiring early.
Then the claiming decision and the account mix, both of which are worth modelling rather than defaulting into.
Sources
Claiming ages and benefit adjustments are published by the Social Security Administration. Required distribution rules are in the IRS RMD FAQs, and Medicare costs at medicare.gov. Walnut is informational and is not an investment adviser. This guide is educational and not personalized financial advice.
FAQ
What is the most common retirement planning mistake?
+
Planning toward a round number rather than from actual spending. A million dollars means nothing without knowing what a year costs you and what income you already have coming from Social Security or a pension.
Why does healthcare get underestimated?
+
Because Medicare starts at 65 and most people retiring earlier have not priced the gap. Marketplace premiums vary widely by income and state, and for an early retiree this is frequently the largest single line in the budget.
What is tax diversification?
+
Holding money across traditional, Roth and taxable accounts so that retirement income can be drawn from different tax treatments. Everything in one bucket removes the ability to manage income against brackets and thresholds.
What is sequence of returns risk?
+
A poor first decade damages a retirement portfolio far more than the same returns arriving later, because withdrawals compound the decline. Holding several years of spending outside equities is the standard defence.
Is holding only cash safe?
+
Not over a 25 to 30 year retirement. Inflation erodes purchasing power steadily, and an all-cash portfolio guarantees that erosion rather than protecting against it.
What about required minimum distributions?
+
Large traditional balances force taxable income out from 73 whether or not you need it, which can push a retiree into a higher bracket than they were ever in while working. Roth conversions in low-income years reduce that.
What is the most overlooked risk?
+
Long-term care, which Medicare largely does not cover and which can be the single largest expense of a retirement. Costing it explicitly beats treating it as a tail the portfolio will somehow absorb.
Which of these should I fix first?
+
The spending estimate, because nothing else can be sized without it. Then healthcare for the years before Medicare, which is the largest uncertainty for early retirees. The claiming decision and the account mix come after, and both reward modelling rather than defaulting.
How often should the plan be revisited?
+
Every few years, and after anything material: a change of job, a house move, an inheritance, a health event. Estimates made decades out are guesses that improve as the date approaches, so treating the plan as fixed is itself one of the mistakes.