SERP Social Security taxation, 401k eligibility, and reporting of income

[RayJJohnsonJr]

A small closely held Corp put in a SERP 10 yrs ago. It's a defined benefit type where the retirement benefit is a fixed amount. Now the Exec is retiring.

The CPA had additional Social Security tax withheld from the Execs salary every year since inception, but I'm not sure how he arrived at the amount. In research, I'm reading it should have been charged on a discount of what the ultimate benefit would be. Is that correct?

I have read that since this compensation is considered to have been earned during the Execs working years, the Exec can defer some of the retirement benefit into the co. 401k, if the 401k permits it. Is that correct?

Lastly, IRS Pub 957 suggests the retirement income is reported on a W-2 in boxes 1 and 11. and no Social Security or medicare tax is withheld. Is that correct?

Thanks so much for any input

Ray