I am preparing taxes for my inactive S-corp just now with zero activities and just realized that that the the March 15 deadline for extension has past. What do I do now?

I already purchased TurboTax for filing my business in 2017 but just realized that I am 3 days past the March 15 deadline for filing extension. What should I do to ensure that my e-file is received by IRS? It has no activities but am keeping the business for now.