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You will deduct all business related expenses. Please see Deduction section on the form 1020S for a list of possible deductions - http://www.irs.gov/pub/irs-pdf/f1120s.pdf Actual deductions would depend on the business specifics.
You may find more detailed information on deductible business expenses in IRS publication 535 - http://www.irs.gov/pub/irs-pdf/p535.pdf
Home Mortgage, Taxes and Insurance if they are your personal expenses are not deductible on the S-corporation tax return.