For how to amend 2016, make selections for the type of software you used and follow the results (linked below).
If you filed a traditional IRA, you can delete your contribution under:
Deductions & Credits
>>>
I'll choose what I work on
>>>
Scroll down to the
Retirement and Investments
section >>> Click
Update/Edit
next to
Traditional and Roth IRA Contributions
>>> the box should be checked for the
Traditional IRA
and you can
uncheck
it >>> the next screen
will ask if you want to delete your entry and you can say
yes.
To enter your SEP contributions, head into:
Business
tab and click
Continue
>>>
I'll choose what I work on
>>>
Scroll down to the
Less Common Business Situations
section >>> Click
Update
next to
Self-employed Retirement
>>> Next, answer
Yes
and enter your pre-tax payroll contributions under Elective Deferrals and the other categories as applicable.
https://ttlc.intuit.com/questions/4381417
