The information balance between HMRC and taxpayers is always in a state of flux. Generally it can be argued that the taxpayer has the upper hand as they know exactly what they have earned and exactly how much they have spent whereas HMRC have to rely either on what they are told by the taxpayer or on what they can obtain from third parties.
However unless it is a specific request that information has to be matched back to an individual record which until relatively recently was nigh on impossible. When I started my career with the then Inland Revenue on top of all the filing racks were boxes full of little cards sent by financial institutions giving details of the interest paid on their accounts.
Every so often a handful of cards were removed and the person traced...
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