I fully appreciate your concerns...I have been in practice a number of years and find the "reality" of what is allowed is not always easily gleaned from the form instructions or IRS publications...the instructions clearly suggest a payment "should" be made...however...it is my understanding that the rules changed years back where an extension will be accepted to avoid a bigger late file penalty even if a payment isn't made....again...this is not tax advice...merely my understanding only and each taxpayer is responsible for doing their own research on their own or with a competent tax preparer....