My employer is supposed to be sending me a W2-C but the deadline is tomorrow and I haven't gotten it yet. Do I go ahead and file now with my original W2?

Yes, you can.

 

However, if you expect chages to your W-2, you may have file an amended return.

 

You can file an extension. However, if you have no taxes due or expect a refund, you are not required to file an extension.

 

If you have taxes due, you have to pay them with your extension,

 

Please read this TurboTax Help topic for instructions on how to file a Federal extension and this one on how to file a state extension.