The filing deadline for Virginia personal returns or extensions is May 1, 2018. Virginia automatically gives you a 6-month extension to November 1, 2018, provided you have already paid at least 90% of your total Virginia tax liability.
If you have already paid at least 90% of your total Virginia tax liability, you do not need to fill out a separate Virginia extension form.
Otherwise, print and mail Virginia Form 760IP or file your extension electronically (you may need Adobe Acrobat reader) by May 1, 2018. To avoid late payment penalties, also include check payment with your printed Form 760IP or pay when you file your extension electronically.
Please see this FAQ for more on filing a state extension: https://ttlc.intuit.com/replies/3300227