Which is mathematically better: a Roth IRA or a Traditional IRA?

A Roth IRA is mathematically superior if your marginal income tax rate during retirement is higher than your current tax rate. A Traditional IRA outperforms a Roth IRA if your tax bracket in retirement is lower than your current tax bracket, provided you reinvest the upfront tax deduction savings.

What are the key differences between a SEP IRA and a SIMPLE IRA?

A SEP IRA is funded entirely by employer or self-employed contributions up to 25% of compensation (subject to statutory limits). A SIMPLE IRA is designed for small businesses with under 100 employees, allowing employee salary deferrals plus mandatory employer matching.

What happens if I contribute more than the annual IRA limit?

Excess contributions to Traditional or Roth IRAs that are not withdrawn before the tax filing deadline face a 6% IRS penalty per year on the excess amount for every year it remains in the account.

When do Required Minimum Distributions (RMDs) begin under SECURE 2.0?

Under the SECURE 2.0 Act, RMDs start at age 73 for individuals reaching age 72 after December 31, 2022, and will increase to age 75 starting in 2033. Roth IRAs have no RMDs during the original account owner's lifetime.

Can I withdraw my money from an IRA before age 59½ without penalty?

Traditional, SEP, and SIMPLE IRAs penalize early withdrawals with ordinary income taxes plus a 10% IRS penalty (25% for SIMPLE IRAs in the first 2 years), unless qualifying for exceptions like first-time home purchases, disability, or SEPP / Rule 72(t). Roth IRA original contributions can be withdrawn at any time completely tax- and penalty-free.

IRA Comparison Calculator

Evaluate Traditional, Roth, SEP, and SIMPLE IRAs side-by-side with taxable savings. Model tax deductions, compounding drag, and net spendable retirement income.

Retirement Profile

Current Age 35

Retirement Age 65

Annual Income 75,000

Starting Balance 25,000

Annual Contribution 7,000

IRS Statutory Cap: 7,000 (8,000 if 50+)

Annual Return (%) 7.5%

Current Tax Rate (%) 24%

Retirement Tax Rate (%) 20%

Reinvest Upfront Tax Deductions in Taxable Account

Allows apples-to-apples comparison by growing annual pre-tax refund savings alongside your Traditional/SEP/SIMPLE IRAs.

Net Spendable Corpus

Roth IRA

100% Tax-Free Cash

Traditional IRA

After-Tax Spendable

SEP IRA

For Self-Employed

SIMPLE IRA

With Match

Taxable Account

After Capital Gains Tax

Side-by-Side Account Breakdown

Account Type	Actual Annual Deposit	Gross Balance	Annual Tax Savings	Retirement Taxes Due	Net Spendable Corpus

Traditional vs. Roth IRA: The Mathematical Decision Framework

Choosing between a Traditional and Roth IRA is fundamentally an arbitrage calculation between your **marginal income tax rate today** versus your **effective income tax rate during retirement**. Neither vehicle is universally superior; each solves for a distinct tax profile:

The IRA Arbitrage Decision Rule:
If (Current Tax Rate) > (Retirement Tax Rate) → Traditional IRA Wins (Take the upfront deduction).
If (Current Tax Rate) < (Retirement Tax Rate) → Roth IRA Wins (Pay tax now, compound tax-free).
If (Current Tax Rate) == (Retirement Tax Rate) → Identical Net Result (if deduction is reinvested).

The greatest error retail investors commit is assuming Traditional IRAs automatically lose because withdrawals are taxed in retirement. When you receive a tax deduction today, that saved money can be invested immediately. As proven in the table above, when you reinvest that annual tax refund, a Traditional IRA maintains mathematical parity or even defeats a Roth IRA if your retirement expenses push you into a lower tax bracket.

Small Business Retirement Plans: SEP IRA vs. SIMPLE IRA

For independent contractors, freelancers, and small business owners, individual IRAs often do not provide sufficient contribution limits. Self-employed accounts allow significantly higher tax sheltering:

SEP IRA (Simplified Employee Pension): Allows contributions up to 25% of net self-employment earnings (or compensation), up to federal limits (69,000). Contributions are made solely by the employer/business owner, offering massive write-offs for profitable sole proprietors.
SIMPLE IRA (Savings Incentive Match Plan for Employees): Designed specifically for businesses with 100 or fewer workers. Employees can defer up to 16,000 (plus 3,500 catch-up if 50+), and the employer is typically required to provide either a dollar-for-dollar match up to 3% of compensation or a 2% non-elective contribution.

Understanding the Taxable Brokerage “Tax Drag”

A standard taxable investment account has no statutory contribution limits or early withdrawal penalties. However, it incurs significant **tax drag** during your accumulation years. In a taxable account, interest, turnover, and dividends are subject to taxation in the year they are received. Over 20 to 30 years, an annual 1.5% dividend yield taxed at 15% to 20% can erode up to 15% to 25% of your final wealth compared to an IRA shelter.

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Frequently Asked Questions

A Roth IRA is mathematically better if your tax rate during retirement is higher than your tax rate today. Because you pay taxes upfront at your current lower rate, every penny of capital gains and compound growth withdraws 100% tax-free. Conversely, a Traditional IRA is superior if you expect your income to fall into a lower bracket in retirement, provided you diligently reinvest the upfront tax deduction savings.

For Traditional and Roth IRAs, the statutory base limit is 7,000 per year, with an additional 1,000 catch-up contribution permitted for individuals age 50 and older (8,000 total). SIMPLE IRAs allow up to 16,000 (plus 3,500 catch-up for age 50+). SEP IRAs allow up to 25% of compensation, capped at statutory ceilings (69,000).

The IRS requires that at least 5 tax years must pass since your first contribution to any Roth IRA before earnings can be withdrawn tax-free, in addition to being age 59½ or older. However, you can always withdraw your original direct contributions at any time without taxes or penalties.

Under the SECURE 2.0 Act, Required Minimum Distributions (RMDs) from Traditional, SEP, and SIMPLE IRAs begin at age 73 (rising to age 75 in 2033). Roth IRAs do not have RMD requirements during the lifetime of the original account owner.

High earners whose Modified Adjusted Gross Income (MAGI) exceeds federal limits cannot contribute directly to a Roth IRA. A “Backdoor Roth” is an IRS-compliant strategy where you make a non-deductible contribution to a Traditional IRA and subsequently convert it into a Roth IRA, avoiding income caps.

Financial Accuracy & Compliance Framework

All projections are modeled according to IRS Publication 590-A/B rules, statutory contribution ceilings, catch-up eligibility at age 50+, SECURE 2.0 Act RMD parameters, and ordinary vs. capital gains tax code provisions. Calculations are validated for mathematical precision.

Disclaimer: This calculation tool is provided for educational and self-directed financial modeling purposes only. It does not constitute tax, investment, or legal advice. Statutory limits and tax laws are subject to legislative adjustments. Consult a licensed certified financial planner (CFP) or CPA regarding your specific tax situation.