S corp - employee solo 401k contribution reporting

[ptax255]

Hello,

Client (owner and employee of S corp) is looking to contribute $23K to the solo 401K as employee portion by year end. The deductions were not made through payroll and now there will not be enough paychecks for it to be made through payroll. My understanding is they can make the lump-sum contribution regardless. My question is how should this be reported on the tax return. 

Should he adjust the W-2 as if the contribution was made through payroll or do I enter it as a deduction in the personal return?

[IRonMaN]

The 401k contribution is still subject to Social Security and Medicare so you can’t just add it to his W-2.  Run a bonus check large enough to cover the 401 contribution and SS and Medicare to generate  zero net check 

[qbteachmt]

The final paycheck dated in 2024 is all you need, even if it is a $0 takehome. Put all bonus, benefit, deduction items here, including personal use of company vehicle, gross up taxes, whatever.