Whenever a taxpayer has timely filed a petition with the Board of Tax Appeals pursuant to the provisions of R.S. 47:1565, 47:1566, and 47:1567 no credit or refund, in respect of the tax for the taxable period involved in the proceedings before the board, shall be allowed or made except:
(1) As to overpayment determined by a decision of the board, which has become final; and
(2) As to any amount collected in excess of an amount computed in accordance with the decision of the board which has become final.