Due to a fault in its service, HMRC's property account service has been miscalculating some capital gains tax (CGT) bills.

As a result many non-residents who use the online system are paying the wrong amount of CGT due on property sales.

HMRC confirmed on its agents forum that the service may even falsely report that there is nothing to pay. The service appears to calculate gains accurately for UK residents.

The problem arises because non-residents can report a rebased value of their UK property rather than its acquisition value.

Non-residents became subject to non-resident capital gains tax (NRCGT) in April 2015, but only for the portion of the gain that arose from that date.

Furthermore, these taxpayers have had to pay normal CGT rates on gains made from 5 April 2019 onwards.

The UK property account service was launched in 2020. It's been found that instead of the service automatically calculating the gain using the rebased value of a property, whatever figure is put in the "initial gain or loss" box is being used.

When asked about the error, HMRC responded:

"The confusion appears to be arising from the assumption the service calculates the gain, whilst in UK resident returns this is correct with non-UK resident returns this is not the case."

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