A Traditional Solo 401k is a version of the Solo 401k where you make contributions with pre-tax income. This means the money you put into the account can reduce your taxable income in the year you contribute, which may lower your current tax bill. Your savings then grow tax-deferred—meaning you won’t pay taxes on investment gains while they’re in the account. You’ll pay taxes later, when you take the money out in retirement. This setup is often chosen by people who expect to be in a lower tax bracket when they retire.