Yes, include Form OW-8-P-SUP-I with Form 511-EF, Oklahoma Individual Income Tax Declaration for Electronic Filing.
Send all of your documentation and Form 511-EF to:
Oklahoma Tax Commission
Oklahoma City, OK 73194
The IRS provides no instructions for filing Form 2210 separately from your tax return. It would do you no good to file Form 8453 - U.S. Individual Income Tax Transmittal for an IRS e-file, since only specific items can be included with that form.
You should try to call the IRS at the number shown in Telephone Assistance. That may or may not be helpful because of staffing shortages, and then your best bet may be to send a copy of your Form 2210, with “COPY” printed prominently on the form, and copies of your documentation, to the address listed under Where Do You File? in the 2021 Instruction 1040. Include a letter of explanation, and ask that your submission be routed appropriately. Provide full contact information.
