You are confusing the terms:
- $18,000 is your elective deferral
- $12,000 is your employer profit sharing contribution
- $30,000 is the sum of your elective deferral and your employer contribution
Regarding your W-2:
- Box 1 = $30,000
- Boxes 3 and 5 = $48,000
- Box 12 = code D, $18,000
Form 1120S should show:
- line 8 [actually line 7 for officers of the company, see comments below] = $30,000
- line 17 = $30,000
Form 941:
- line 2 = $30,000
- Lines 5a and 5c = $48,000
I'm not familiar with Form 940, so I will refrain from commenting on that.
