First you did not pay to efile since efiling is free when using the Online version ... the fee is for the use of the program to complete a tax return that can be filed even if you must mail in the return  ... there is no guarantee that you will be able to efile.

Next  there is no such thing as a 2 digit code on a W-2 ... so did you mean the 2 letter state abbreviation like OK for oklahoma?   What is the exact error message?

No. First, I know the difference between a state letter code and a two digit numeric code. Second, it was not an error message. It was part of the questions when completing the process. When I entered the one digit, the program came back with a request for a 2 digit code from 'control number box d' on the W2. It stated if I didn't have a 2 digit number in that box, I could not efile and said to print and mail, which I did.  

Go back and blank it out.  Skip it.  W2 box d Control number is not needed.  See
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Guess it's too late now to clear it and efile since you already mailed it.  Sorry, next time ask first before mailing.  

https://ttlc.intuit.com/replies/4417180