Your extension only gave you extra time to prepare and file your Form 1040---it did not give you extra time to pay your tax due. You were supposed to pay the estimated tax due by April 15. Pay asap. TurboTax will not calculate your interest or penalties for late payment; the IRS will bill you later after they receive your return and the amount that you pay now.
If you have federal tax due you can pay by mailing your payment with the 1040V voucher, (which has the address printed on it, having the payment taken out of a designated bank account, or you can pay directly on the IRS website.
https://www.irs.gov/payments
https://ttlc.intuit.com/community/tax-payments/help/how-can-i-pay-my-federal-taxes/00/26212
https://ttlc.intuit.com/community/tax-payments/help/how-do-i-pay-my-irs-tax-due-with-a-check-or-mone...
To apply for a payment plan with the IRS
Apply Online for a Payment Plan
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
