The account set up to hold the money that the European Commission instructed Ireland to collect in so-called back taxes from Apple declined in value by €36 million last year.
According to figures published by the Department of Finance, the value of the Ireland Apple Escrow Fund stood at €13.98 billion at the end of 2020.
The decline in value was attributed mainly to 'the current negative interest rate environment and negative yields on highly rated euro-sovereign, quasi-sovereign bonds and fund operating expenses'.
The low rate environment is being supported by the European Central Bank through its policy of buying bonds in order to keep the borrowing costs of EU governments low.
That policy was extended at the onset of the pandemic as countries borrowed heavily to support their economies.
However, it means all investors in government bonds are getting low or negative returns.
The Ireland Apple Escrow Fund remains in existence despite a ruling by the EU's General Court last year ruled that Ireland did not give Apple illegal state aid.
The ruling overturned a previous European Commission decision that the iPhone maker owed Revenue €13.1 billion in back taxes.
The addition of interest saw that figure rising to €14.3 billion.
The Commission has since lodged an appeal with the European Court of Justice challenging the General Court judgement.