I filed a tax extension with chk to cover est. I completed my turbo tax and want to know if I can file on-line and how to send the extra money owed?

[xmasbaby0]

When you requested your extension you were supposed to pay your estimated tax due.  Did you enter the payment you made into your tax return?  Go to Federal>Deductions and Credits>Estimates and Other Taxes Paid>Other Income Taxes 

E-filing is open for 2018 returns until October 15, 2019.  If you still have more tax due when your return is ready to be filed, then you can mail in a check or money order with the return or 1040V voucher, or you can pay directly on the IRS site:

https://www.irs.gov/payments