"I read the other Turbo tax reply said : Sep contribution should be box 12 on W-2? I confused."
Only salary deferrals to a SARSEP (SAlary Reduction SEP) established before 1997 are reported on a W-2. Since you are asking the question now, I'm sure it's a safe bet that you do not have such a SARSEP, so nothing about a SEP contribution is reportable on a W-2. Some employers will mention the SEP contribution in box 14 of a W-2, but that's for your information only and is otherwise not reportable.
To be eligible for a SEP contribution, the employee must meet the eligibility requirements that you have in specified in the SEP plan. If both you and your wife meet the eligibility requirements, the contribution as a percentage of wages is required to be the same for both of you. For example, if the contribution percentage is 25% (the maximum permissible), you have wages totaling $60,000 and your wife has wages totaling $40,000, the S corp must make a $15,000 contribution to your SEP-IRA and must make a $10,000 contribution to your wife's SEP-IRA. Of course the S corp could elect a smaller percentage for the contributions if it so chooses as long as the percentage is the same for all eligible employees.
You typically can have only one plan, so if you establish a solo 401(k) then you would not establish a SEP plan. The employer contribution for a solo 401(k) can be no more than the contribution to a SEP plan, but might be less because with a Solo 401(k) plan the employee can make elective deferrals (which would need to be reported in box 12 of the employee's W-2) and total additions are not permitted to exceed compensation.
Contribution limits to a SIMPLE IRA are subject to different limits. In most cases a Solo 401(k) would make more sense than a SIMPLE IRA, but I suggest reviewing IRS Pub 560 for the detailed differences. That publication consists of 43 pages that are too much to repeat here.
