"In any case, where for any prescribed accounting period there has been paid or credited to any person ... b) as being due to him as a VAT credit, an amount which ought not to have been so paid or credited or which would not have been so paid or credited had the facts been, or been, as they later turn out to be, the Commissioners may assess that amount as being VAT due from and for that period, and notify it to them accordingly."
"An appeal shall lie to the tribal with respect to any of the following matters ... (p) (an assessment) ..."