How do I calculate the profit sharing amount for my individual 401K as a sole proprietor?

Hello community. I am thinking of opening an individual 401K (95% of my income is 1099, self-employment and 5% is from an LLC as passthrough). My tax extension deadline is 10/15/25. I know that I cannot make elective deferrals and catch up contributions retroactively for 2024. However, I understand that I can still make the profit sharing contributions (approx 25% of net self-employment inc.). TT has the Maximize button for the individual contributions BUT I don't see how I can calculate the Employer (Profit Sharing) contributions to see how much it might impact my State Tax liability for California. From other TT posts, I learned there is no impact on Federal taxes in terms of a deduction. I would need to know how to make this calculation anyway for the 2025 tax year so looking for some guidance. Thanks.

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