Giles Hembrough, from Bristol, was sent the notice for a 16 digit sum after his tax code changed.
The notice from HMRC said “Although we are changing your tax code you may still not pay enough tax by 5 April 2017. We think the amount you owe HMRC is £14,301,369,864,489.03. Almost double the size of the UK economy or 46 billion iPhones.
Fortunately the tax man acknowledged the error.