I guess you are trying to say you’ve paid HMRC too little and you think its HMRC’s fault?
Anyway in any case, if you have underpaid/overpaid VAT because of a mistake in your past VAT return, correct it in your next regular return.
If the fault lies with HMRC there is no interest or penalties. If the fault is you there may be interest or penalties.
Further rules need to be taken into account ie You can adjust your next VAT Return if the net value of the errors is £10,000 or less. You can also adjust your next VAT Return if your error amount is up to 1% of your box 6 figure (up to a maximum of £50,000). You must report the error to HMRC if it’s above the reporting threshold.