I used TurboTax last year like I’ve done for the last 15 yrs. I submitted the extension form through TT for the first time and thought everything was fine. After I sent my return in October I got a bill from the IRS that I owed $13 because I submitted my return late! Thankfully, I only owed $115 this year so the hit was minimal. Somebody, somewhere, screwed up, so I don’t have high hopes that this new rollout will be easy peasy at all.
Extension of time to file DOES NOT extend the time you have to pay tax in full.
April 15 (or the first Federal workday after that) is the due date for being paid in full to duck penalties.
Last year (May/June) the IRS sent me a bill for under with holding of $165 and I paid it. In October I got a check from them for $165.
I guess the IRS f*cked up and can't be trusted to do anything right.