Remember, there are two ways to get funds into your Solo 401k plan:
Rollovers can come from almost any retirement plan (traditional IRA, 401k, 403b, TSP, pension plan, etc). Rollovers can be partial or full and can happen on any schedule and in any amount.
Contributions come from earnings from your business.
Here's how to contribute funds to your Solo 401k:
Determine contribution type (pretax/Roth/employer/employee)
Move funds from business or personal account to Solo 401k bank/brokerage account (make sure you keep pre-tax money in pre-tax bank/brokerage account and Roth contributions in Roth bank/brokerage account)
Maintain a separate bank or brokerage account for each plan participant
Maintain a separate bank or brokerage account for each type of tax-classified funds. This may mean you have a pre-tax, after-tax, and Roth account
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