Can I make an additional contribution in 2018 for to my 2017 Simple IRA to reduce the amount of taxes I owe? If so what are the limits and deadlines?

[LinaJ2018 · Accepted solution]

It is possible if you are self-employed. 

If you are self-employed, you must deposit your salary reduction contributions within 30 days after the end of the tax year. For most people, this means salary reduction contributions for a year must be made by January 30 of the following year.  You must deposit your employer contributions by the due date (including extensions) of your federal income tax return for the tax year that includes the last day of the calendar year for which you made the contributions. For most people, this means employer contributions for a year must be made by April 15 of the following year, or by October 15 if on an extension.  Please see Self-Employed

If you are an employee, the latest date to make a contribution for the year of 2017 is December 31, 2017. 

If you are an employer, contributions made on the part of the employer are due by the business' filing due date for the tax year - usually April 15, or Oct. 15 if there is an extension