HMRC has received £342m from Switzerland as a result of the Swiss-UK tax deal which came into force on 1 January.
This payment is being made by Swiss banks in advance of the one-off charge being levied on their customers.
Under the deal, the Swiss are taxing the bank accounts of UK citizens and transferring the money directly to the Treasury without revealing the identity of account holders.
The £342m is just the first instalment, however the Revenue is expecting the deal to add £5bn of previously unpaid tax to their coffers.
Current and future tax liabilities in Swiss accounts will be covered by a new withholding tax of 48% of income.