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
