Form 1127 is filed with the Internal Revenue Service (Attn: Advisory Group Manager) for the area where you maintain your legal residence or principal place of business. See Pub. 4235, Collection Advisory Offices Contact Information, to find the address for your local advisory group.
Refer to IRS instructions: Form 1127 Application for Extension of Time for Payment of Tax Due to Undue Hardship and TurboTax article: Filing Your Taxes Late.