To request an extension for filing a federal tax return you will need to complete IRS Form 4868. E-filing of the extension request will be available from TurboTax in mid-March. There are no extensions for tax payments since any taxes owed on a 2018 tax return must be paid on or before April 15, 2019 to avoid a failure to pay penalty.
See this TurboTax support FAQ - https://ttlc.intuit.com/questions/1901031-how-do-i-file-an-irs-extension-form-4868-in-turbotax-onlin...
TurboTax website for Easy Extension - https://turbotax.intuit.com/irs-tax-extensions/
You only need the IRS Form 4868 to file for an extension. To pay any taxes owed you can use the IRS website for tax payments and select Direct Pay. Use IRS Direct Pay to make a full or partial payment on your taxes in order to receive an extension without having to file Form 4868 - https://www.irs.gov/payments/direct-pay
