How Taxes on 401(k), IRA, and Roth Withdrawals Affect How Long Your Money Lasts

Here's a quiet problem hiding in a lot of retirement plans. You look at your account, see $600,000, and tell yourself that's $600,000 you can spend. It isn't. Depending on where that money sits, a chunk of every withdrawal may belong to the tax collector, and that changes how long the rest of it lasts.

This article explains how taxes interact with different kinds of accounts, shows how much they can shorten your timeline, and covers a few rules that are worth knowing before you start taking money out.

Three Kinds of Money

Most retirement savings fall into one of three buckets, and each one is taxed differently.

• Pre-tax accounts, such as a traditional 401(k) or traditional IRA. You got a tax break when the money went in, so withdrawals are taxed as ordinary income.
• Roth accounts, such as a Roth IRA or Roth 401(k). You paid tax on the money going in, so qualified withdrawals generally come out tax free.
• Taxable accounts, like a regular brokerage account. You've already paid tax on the contributions, and you generally owe tax only on the gains when you sell, often at lower rates.

The key point is that a dollar in each bucket is not worth the same amount of spending money. That's why calculators that ignore taxes can give you an answer that's too rosy.

Gross vs. Net: The Gap Calculators Miss

When you plan your retirement, you think in terms of net income, the amount you can actually spend. But when you withdraw from a pre-tax account, you take out the gross amount, and tax comes off the top. To end up with a certain net, you have to withdraw more.

The formula is simple: divide the net amount you want by one minus your tax rate. If you want $3,000 a month and your effective tax rate is 15%, you need to withdraw $3,000 divided by 0.85, which is about $3,530.

Here's how that plays out for a $600,000 pre-tax portfolio earning 5% a year, where you want $3,000 a month to spend after tax:

The spread is large. Same balance, same return, same spending. Yet the flat-withdrawal runway runs from about 36 years in the tax-free case to about 19 and a half in the 25% case. That's a difference of more than sixteen years, caused entirely by the account type and the tax rate.

Effective Rate vs. Marginal Rate

A common mistake is to use your top tax bracket as your tax rate. In reality, the tax system is progressive, so each slice of income is taxed at its own rate, and the first slice is often not taxed at all thanks to the standard deduction. Your effective rate, meaning the total tax divided by your total income, is usually much lower than your top bracket.

In retirement, your effective rate depends on how much taxable income you have across all sources, including withdrawals, pensions, and part of your Social Security. In the United States, up to 85% of Social Security benefits can become taxable depending on your total income, so the more you withdraw from pre-tax accounts, the more of your benefits may be taxed as well. A rough estimate is better than none, but if you can, work through a sample tax return for a typical year in retirement to get a more realistic rate.

Roth vs. Traditional in Practice

Let's say you have two $300,000 buckets, one Roth and one pre-tax, and each needs to provide $1,500 a month after tax. The Roth bucket pays out $1,500 a month. The pre-tax bucket, at an effective rate of 15%, has to pay out about $1,765 a month to net the same $1,500.

At a 5% return and flat withdrawals, the Roth bucket lasts about 36 years, while the pre-tax bucket lasts about 25. Same starting balance, same spending, and an 11-year gap. This is why many people treat Roth money as especially valuable. It's flexible, and every dollar of it can be spent.

That doesn't mean pre-tax accounts are a bad deal. The tax break on the way in is real, and you may well be in a lower bracket in retirement than you were while working. The point is simply that you should count each bucket for what it's really worth, after tax.

Required Minimum Distributions

Pre-tax accounts come with a catch. At some point, the government wants its tax, so it requires you to start taking minimum withdrawals each year, called required minimum distributions, or RMDs. Currently the starting age is 73 for most people, and it's scheduled to rise to 75 for younger savers, so check the rule that applies to your birth year.

These withdrawals are required whether you need the money or not, and missing one triggers a steep penalty. They also add to your taxable income, which can push you into a higher bracket and increase the tax on your Social Security. Roth IRAs don't have RMDs during the original owner's lifetime, and Roth 401(k)s were changed to match, which is another reason Roth money is handy for managing taxes late in life.

Does the Order You Withdraw Matter?

Yes, it can. A traditional rule of thumb says to spend taxable accounts first, then pre-tax accounts, and leave Roth money for last, since Roth money can keep growing tax free. But that isn't always best. Some people do better by drawing a little from pre-tax accounts each year to stay in a lower tax bracket, rather than letting RMDs push them into a higher one later. Others convert part of their pre-tax savings to Roth in low-income years, paying some tax now to reduce it later.

Which approach works for you depends on your income, your bracket, and your timeline, and it's one of the areas where a conversation with a tax professional can pay for itself.

Don't Forget State Taxes and Early Withdrawal Penalties

Two more items can quietly change your numbers. Some states tax retirement income and others don't, so your effective rate might be higher or lower than a federal-only estimate. And if you take money from a 401(k) or IRA before age 59 and a half, there's generally an extra 10% penalty on top of regular tax, with some exceptions.

Putting Taxes Into Your Calculator

Most basic calculators don't handle taxes, but you can add them yourself in three steps. First, decide what net amount you want to spend each month. Second, estimate your effective tax rate for each account type. Third, divide your net amount by one minus that rate to get the gross withdrawal, and enter that number. If you have several buckets, run them separately, then compare how long each one lasts.

Try It With Your Own Numbers

Taxes are one of the easiest factors to overlook and one of the easiest to fix once you see them. The how long will my money last calculator on this site lets you try different withdrawal amounts in a few minutes, so you can compare a tax-free withdrawal with a taxed one and see the difference for yourself. It's a quick way to find out how much of your balance is really yours to spend.

This article is for educational purposes only and is not financial, tax, or investment advice. Tax rules change and depend on your individual situation. Projections are estimates based on assumptions, and actual results will vary. Consider talking with a qualified tax or financial professional about your specific situation.