Turbotax doesn't support form 843 and in any case it can't be filed with your return regardles of whether e-filed or mail
look at 1040 instruction for mailing address page 113 refund column
https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
filing instructions
the service center where you would be
required to a file a current year tax return for
the tax to which your claim or request
relates. See the instructions for the return
you are filing.
