Thanks for answering! I am now trying to fill in form 4868, but it doesn't include instructions on how to calculate one's tax liability. I understand I have to retrieve this number after filling in form 1040 (line 63). But I usually use TurboTax to figure out my taxes, instead of filling in form 1040 by hand. So how do I, at this point, figure out what my tax liability is in order to fill in the tax extension form?
