The cover/summary page with the \"Electronic Filing Instructions\" for my KY state return indicates I'm to \"sign and date Form 8879-K within 1 day of acceptance\". Why?

[daharrod]

I thought Form 8879 was needed only when a 3rd party completing a return.

[JohnW152]

Not necessarily. 

If you filed your own with a federal PIN, Form 8879-K isn't required. 

But if you filed your own return without the PIN, sign and date the form, and retain it for three years.  You don't need to mail it, just keep it with your tax records.

The Filing Requirements on the second page of Form 8879-K, Kentucky Individual Income Tax Declaration For Electronic Filing state:

• Federal/State E-file With a Federal PIN—For returns filed via this method, an 8879-K is not required. 
• Federal/State E-file Without a Federal PIN—For returns filed via this method, an 8879-K is required to be completed. Do not mail this form. Electronic return originators (EROs) must retain them for a period of three years. 
• Online Filing—For returns filed via this method, an 8879-K is required to be completed and retained for a period of three years. Do not mail this form.