Calculation of interest: The issue date
When the issue date of an officer’s assessment is notified to the computer via input of a VAT645 to VALID, see VAEC8720, a further interest calculation date is set 30 days from this time. You can view this date on the “OA Details” screen on VISION. It is most important that this date is correct otherwise the taxpayer may not get a full 30 days in which to pay the tax amount liable to interest. You should therefore make sure that the issue date noted on the VAT645 is the actual issue date of the assessment.
Once the date has been input to the computer it is not possible to change it. Therefore if the date is later found to be incorrect and as a result the taxpayer has been charged too much interest, it will be necessary to adjust the interest liable amount using the VAT663 procedures, see VDIM6000.