Filing S Corp taxes but forgot to pay quarterly and didn't use payroll, didn't file W2 or W3 in 2017, can I file all forms and pay all quarterly now?
Yes. You need to complete the W-2/W-3 and 941 filings for 2017, in addition to any state withholding filing required. And, on the 2017 SCorp return, you will show as expenses the gross salaries/wages paid in 2017 along with the employer portion of the social security and Medicare taxes that were due on those wages. Any federal or state income taxes withheld from payroll are not deductible expenses to the SCorp (this is because they are employee payments and you are deducting the gross pay as an expense.) BUT, if you are an employee of the SCorp, then you would report the federal and state taxes withheld, along with your salary/wage income on your personal return from the W-2 that you are soon to create.
Note that when the SCorp files the 941 forms, there more than likely will be penalties and interest assessed by the IRS for late payments.