How do i amend my extension

[rmscarpe]

can you amend an extension

[CatinaT1]

You can not amend an extension.  As long as you filed one the amounts listed are only estimates.

[fanfare]

If you e-file Form 4868 and mail a check or money order to
the IRS for payment, use a completed paper Form 4868 as a
voucher. Please note with your payment that your extension request
was originally filed electronically.