Filed an extension on April 15th, 2019 for my 1099- misc. I just filed and I owe $587 dollars. Do I send a check for $587 or do I add some kind of interest or fee?

[Critter]

Send only what the return says you owe....the irs/state will bill you later for any penalty or interest.

[DoninGA]

You just pay the taxes owed using the method of payment you selected.  If you are paying taxes after the due data of April 15, 2019 for a 2018 tax return, the IRS will send you a bill in the mail for any penalty and interest after they receive the tax return and tax payment.

[Anonymous]

you don't even need to send a check.  the IRS and most states allow payment through their website.    paying through your bank account is free. there are fees if you wish to use a debit or credit card.   at the end there will be a means of either printing a receipt for proof or even getting a verifying email.     if you do decide to mail a check  use a method where you get proof of delivery and make sure that the TT filing instructions are followed for where to mail and what info should be on the check also include 1040-V

what you filed was not a 1099-misc but your 1040. 

since the payment was due 4/15/19 expect a bill from the tax authorities for interest and possibly penalties