Contributions to Solo 401k

[Nitin Dhiman]

I've read through quite a few of the existing discussions on Solo 401k on this forum. Brilliant stuff. However, I have a very specific question regarding allowable contributions to the Solo 401k.

If I have a side business (outside of my regular day job) as a sole proprietor, do I need to limit my contributions to my Solo 401k to the income or profit from my business? For example, if I make $10k in revenue from my side business, can I only contribute up to $10k into the Solo 401k? Or am I able to contribute, say $40k (income from other sources) so that I can maximize my Solo 401k while deferring taxes on the extra $30k contribution?

Thanks!

Nitin