The biggest tax benefit of any retirement account is reducing your taxable income today. Every dollar you contribute to a pre-tax retirement account is a dollar that doesn’t get taxed this year. For a business owner in the 32% bracket, a $50,000 contribution saves $16,000 in federal taxes alone. The question is which account lets you put away the most while fitting your business situation.

For solo operators and business owners with no employees other than a spouse, the Solo 401(k) is usually the strongest option. You can contribute as both employee and employer, which for 2025 means up to $23,500 in employee deferrals plus up to 25% of your net self-employment income as an employer contribution, for a combined maximum of $70,000. If you’re 50 or older, catch-up contributions push that even higher. You also get the option of Roth contributions on the employee deferral side if you want tax-free growth instead of a deduction now.

The SEP IRA is simpler to set up and administer. You can contribute up to 25% of net self-employment income, maxing out at $70,000 for 2025. The downside is that there’s no employee deferral component and no Roth option. If your income is high enough to max out the employer contribution, a SEP IRA and Solo 401(k) produce similar results. But at lower income levels, the Solo 401(k) lets you shelter more because of that employee deferral piece. One important consideration with SEP IRAs is that if you have employees, you must contribute the same percentage for them as you do for yourself.

SIMPLE IRAs work for businesses with up to 100 employees. The contribution limits are lower at $16,500 for 2025 with a required employer match. These are easier to manage than a full 401(k) plan but the tax shelter is smaller. They make the most sense for businesses that want something straightforward and are willing to trade maximum contribution room for simplicity.

Defined benefit plans are the heavy hitter for high-income owners who want to shelter the most money possible. Depending on your age and income, annual contributions can exceed $200,000. The tradeoff is higher administrative costs, required actuarial calculations, and mandatory funding each year. These work best for established businesses with consistent, high profits where the owner wants to aggressively reduce taxable income for several years leading up to retirement.

The right choice depends on a few things. How much profit does the business generate? Do you have employees you’d need to cover? How much administrative complexity are you willing to handle? Are you optimizing for maximum deduction now, or do you want Roth flexibility for tax-free withdrawals later? These are all factors that change the answer from one business to the next.

Getting the account choice right is important, but it’s only one piece of a broader tax advisory strategy. Retirement contributions interact with your entity structure, your salary versus distribution split (if you’re an S-corp), and your overall tax picture. Maximizing one piece without considering the others can leave money on the table.

Clean financials make all of this easier to plan. When your small business bookkeeping is current and accurate, you can see mid-year where your profit is trending and make contribution decisions before December instead of scrambling during tax season. The business owners who get the most out of retirement accounts are the ones who plan ahead with real numbers, not estimates.