Forgot to take tax deduction for SEP contribution

Owner has S Corporation, and takes W-2 pay annually.   Only other employee of corporation is wife, who also receives W-2.    Owner made SEP contributions for several past years, but did not take tax deduction on corporate tax return.  

Can owner prepare revised tax returns for past year to claim deduction. 

Can owner take tax deduction in current year for past years accumulated missed tax deductions; i. e. can it be carried forward.   

What other options are available to capture past years missed tax deductions

Suppose in one of the past years, the SEP contribution was greater than 25% of the W-2 amount, or exceeded the dollar limit for SEP contributions.    Can the excess be carried forward.  

This calls for professional tax advice. The Owner needs to hire someone to help solve this problem.

Bill Presson is correct.

From the content of your first three questions, it indicates you need a tax professional to correct these to the extent possible.

For the last question, Excess SEP IRA contributions not returned by your tax filing date including extensions are a plan error. This is most definitely not an inexperienced DIY correction process. You need to engage an experienced professional retirement plan specialist. Tax professionals seldom have the knowledge or experience necessary.