@Skylane Speaking of confessions, how many of us can remember the time when the catechism taught was that IRS could reject an extension request if the estimated tax owed was not paid with the 4868?  I still catch myself filling them out to show no balance due when that is unlikely.  The instructions to Form 4868, however, show that redemption and forgiveness is available:

Line 7—Amount You’re Paying
If you find you can’t pay the amount shown on line 6, you can still
get the extension. But you should pay as much as you can to limit
the amount of interest you’ll owe. Also, you may be charged the late
payment penalty on the unpaid tax from the regular due date of
your return.