How Buffett’s 90/10 Strategy Would Work for a 65-Year-Old With $600,000 in an IRA and $2,800 in Monthly Social Security

Warren Buffett has made clear how he wants his wife’s money handled after his death. In a 2013 letter to Berkshire Hathaway shareholders, he said the trustee’s instructions could hardly be simpler: keep 10% in short-term government bonds and 90% in a very low-cost S&P 500 index fund. No stock picking, no bond ladder, no annuity.

That guidance was meant for a widow who would not need to spend the principal. Most new retirees are in a very different situation. So let’s apply the 90/10 approach to a more typical case: a 65-year-old single retiree with $600,000 in a traditional IRA and $2,800 a month from Social Security. The key questions are how much income that person can spend each month and how much tax the IRS would collect.

What the portfolio would look like

Applied exactly, the IRA would hold $540,000 in an S&P 500 index fund and $60,000 in Treasury bills. The fund Buffett has mentioned more than once is Vanguard’s S&P 500 ETF, which recently closed at $704.78 a share and paid $7.43 a share in dividends over the past 12 months, a yield of about 1.05%. Three-month Treasury bills were yielding 4.21% based on Treasury data.

That means the portfolio’s own income is not especially large. The stock portion produces about $5,670 a year, while the bill portion adds about $2,530. Combined, that works out to roughly $8,200 a year, or about $683 a month, before any shares are sold.

Buffett’s point was never that dividends alone would fund retirement. His argument was that stocks should grow faster over a long retirement, while the 10% in bills provides a spending reserve so the retiree is not forced to sell stocks after a market drop.

How the spending would work

Using the standard 4% withdrawal rule as a starting point, $600,000 would support $24,000 a year, or $2,000 a month, from the IRA. Add the $2,800 monthly Social Security payment, and total cash flow rises to $4,800 a month, or $57,600 a year.

In practical terms, the $24,000 IRA withdrawal would be covered partly by the $8,200 in dividends and interest. The remaining $15,800 would come from selling roughly 22 shares of the index fund at today’s price. If stocks have a down year, the retiree could instead draw the entire $24,000 from the $60,000 Treasury-bill cushion and leave the stock fund untouched. That reserve would cover about two and a half difficult years.

If the retiree wants more than $2,000 a month from the IRA, the math changes quickly. A 5% withdrawal equals $2,500 a month and has historically held up over 30 years in most periods. A 6% withdrawal, or $3,000 a month, has exhausted portfolios in the worst 30-year stretches on record.

What the tax bill would be

This is where the plan becomes more favorable than many people expect.

Social Security is taxed based on other income plus half of the benefit. For this retiree, that means $24,000 in IRA withdrawals plus half of $33,600, which equals $40,800. Since that is above the $34,000 threshold for a single filer, part of the benefit becomes taxable. Using the IRS worksheet, $10,280 of the $33,600 Social Security payment is taxed, while $23,320 remains tax free.

That puts total federal income at $34,280, consisting of $24,000 from the IRA and $10,280 in taxable Social Security.

Next come the deductions. For the tax year referenced here, the standard deduction for a single filer is $16,100. Anyone 65 or older gets an additional $2,050. A newer tax law also gives people 65 and older an extra deduction of up to $6,000 through 2028, which this retiree receives in full because income is well below the $75,000 phaseout level. Together, those deductions total $24,150.

That leaves taxable income of $10,130. All of it falls within the 10% bracket, so the federal tax bill comes to about $1,013 for the year.

In other words, a retiree spending $4,800 a month, or $57,600 a year, would owe the IRS only about $1,000. That is an effective federal tax rate of less than 2% on cash flow. State taxes would vary by location, and most states do not tax Social Security.

What happens at age 73

There is one important future milestone. Starting at age 73, the IRS requires withdrawals from a traditional IRA every year, whether the account owner needs the money or not. If the account has grown to around $800,000 by then, the first required minimum distribution would be about $30,200. That is higher than the $24,000 withdrawal in this plan, which means income would rise, more Social Security would become taxable, and the tax bill would increase.

Many advisers recommend converting part of the IRA to a Roth in the years between 65 and 73, using up room in the 10% and 12% brackets. For this retiree, that could mean roughly $22,000 a year in conversions taxed at 12% or less now, instead of later when required distributions are added on top of Social Security. The amount is limited because each conversion also increases taxable Social Security income until as much as 85% of the benefit becomes taxable. Roth money, meanwhile, has no required withdrawals and can be taken out tax free.

Where the strategy can fall short

Buffett’s 90/10 approach is designed for someone with a very long horizon and the ability to endure a 30% market decline. A 65-year-old withdrawing 4% a year may be able to tolerate that, but only barely. The $60,000 bond cushion is what makes the plan workable. If that reserve is spent on a major expense early on, such as a kitchen remodel, the portfolio effectively becomes a 100% stock strategy with a fixed withdrawal rate, which is a very different and riskier setup.

The other issue is yield. At about 1.05%, the S&P 500 does not generate much income if the goal is to live mostly off dividends rather than sell shares. A 10-year Treasury is yielding 4.95%, and many retirees may prefer a larger bond allocation than Buffett’s 10%. That is a reasonable choice. It would likely leave them with less money at 85, but it may also help them sleep better.

The takeaway

For a single 65-year-old with $600,000 in an IRA and $2,800 a month in Social Security, Buffett’s 90/10 framework would generate about $4,800 a month in spending money and a federal tax bill of roughly $1,000 a year, helped by the senior deduction and the way Social Security is taxed. The main task over the next several years would be preserving the $60,000 cushion and moving money into a Roth while the tax rate remains relatively low.