“ 78 Interest in certain cases of official error (1) Where, due to an error on the part of the Commissioners, a person has- (a) accounted to them for an amount by way of output tax which was not output tax due from him and, as a result, they are liable under section 80(2A) to pay (or repay) an amount to him, or … (c) (otherwise than in a case falling within paragraph (a) … above) paid them by way of VAT an amount that was not VAT due and which they are in consequence liable to repay to him, …. then, if and to the extent that they would not be liable to do so apart from this section, they shall pay interest to him on that amount for the applicable period, but subject to the following provisions of this section. … (3) Interest under this section shall be payable at the rate applicable undersection 197 of the Finance Act 1996 . … (10) The Commissioners shall only be liable to pay interest under this section on a claim made in writing for that purpose.”