“(3) … an amount equal to the amount which a designated HMRC officer determines, to the best of that officer's information and belief, as the understated tax ... (4) “The understated tax” means the additional amount that would be due and payable in respect of tax if— … (b) in the case of a notice given by virtue of section 219(4)(b) (cases where the DOTAS requirements are met), such adjustments were made as are required to counteract what the designated HMRC officer determines, to the best of that officer's information and belief, as the denied advantage; … (5) “The denied advantage”— (b) in the case of a notice given by virtue of section 219(4)(b), means so much of the asserted advantage as is not a tax advantage which results from the chosen arrangements or otherwise, …”
“We’ll calculate the amount to the best of our information and belief. If we don’t have all the information we need to establish the amount, then the amount shown in the accelerated payment notice may not be the same as the amount when your compliance check is complete … If the amount in the accelerated payment notice is more than the amount we find to be due once your compliance check is complete … we’ll normally repay any amount that you’ve overpaid. We’ll also pay you any interest that is due to you in respect of the amount overpaid.”