Late filing S-corp designation and quarterly withholdings

Hello!

 

I work as a contractor and currently live outside of the US. Before I left, I set up an S-corp and my invoices have been going to a bank account owned by the business. I didn't make any quarterly withholdings, and only now discovered that the paperwork for the S designation was never sent to the IRS.

What should I do now? I know I can file for a late designation, but I also need to account for the missed quarterly withholdings. Any advice will be appreciated, thank you!