Can a high-earning solo use a defined-benefit or cash-balance plan to save more?

Yes, and it's one of the most powerful tools for a high-income solo who wants to shelter far more than a Solo 401(k) allows. A defined-benefit or cash-balance pension plan can permit contributions well into the six figures depending on your age and income, because the limit is based on funding a future retirement benefit rather than a fixed annual cap. The older you are and the higher your stable profit, the larger the deductible contribution. These plans require an actuary, annual filings, and a commitment to fund them consistently for several years, so they fit someone with strong, predictable earnings — think a consultant or specialist netting $300,000+ who has already maxed other accounts. Many high earners pair a cash-balance plan with a Solo 401(k) for even more. Because the setup is complex, work with a third-party administrator before committing.