How much can I contribute to my solo 401k this year?

[Dan Rudolph]

My wife and I are the sole proprietors of the business that that sponsors our solo 401k (unincorporated sole proprietorship).  That business will probably make a total of $30K in 2018.  I understand that this calculates to a maximum contribution of $27,880.

However, does this mean that:

1. I can contribute $27,880 if my wife contributes nothing?
2. I can contribute only $27,880 / 2 = $13,940 regardless of what my wife does?
3. We can *both* contribute $27,880?

Thanks for any help you can provide.

[Ashish Acharya]

, 

Correct me if I am wrong @Dmitriy Fomichenko and @George Blower

You are considered both "employer and employee" for your Solo 401k, thus, you can contribute lessor of 

• 1) 55k or 
• 2) 100% of your SE income plus 6k catch up. 

As an elective deferral, you can contribute 18.5k +6 catch up 

As an employer contribution (profit sharing contribution) on your behalf, based on your SE income, you can contribute =  $5,576

Max Plan Contribution rate	25%
SE Contribution rate	20%
CY FICA base	$128,400
CY SE tax	15.3%
Net Income from Self Employment	$30,000
Earning sub to SE	$27,705
SE Tax	$4,239

Schedule C	$30,000
Less 1/2 SE tax	$2,119
Net	$27,881
Contribution	$5,576

Total contributed is 24,076 + 6k if you are above 50. 

You can deduct this amount as an adjustment to income on Schedule 1line 28 (new tax form)