The production of thousands of special commemorative Brexit coins has been put on hold amid continuing uncertainty over when the UK will leave the EU.
The Royal Mint had been asked to make new 50p pieces featuring the 31 October date on which the UK was due to leave and a message of "Peace, prosperity and friendship with all nations".
The Queen approved the order at a recent Privy Council meeting.
But the Treasury said the initiative had now been "paused".
The UK was due to leave the EU at the end of the month but, amid continuing political deadlock in Parliament, the bloc agreed on Friday to further delay the UK's departure.
It is set to make a decision on the length of the extension to the Brexit process next week.
Up to 10 million new coins were reportedly being made ready for the 31 October deadline, in a project championed by Chancellor Sajid Javid since he took office in July.
His predecessor Philip Hammond had planned a limited edition of about 10,000 commemorative 50p coins to be sold to collectors for £10 each.
But Mr Javid ramped up the plans this summer in what was seen as a symbol of the UK's determination to leave the EU and forge a different relationship with the EU.
Under plans signed off by the Queen earlier this month, three different types of 50p Brexit coins were to be made from gold, silver and cupro-nickel - a mixture of copper and nickel.
The gold coins were not intended to enter mass circulation.
But the silver and cupro-nickel ones were set to become legal tender.
The design, featuring the monarch's head and a standard inscription on one side and the special message and date on the other, was approved at a meeting of the Privy Council on 8 October - attended among others by Leader of the House of Commons Jacob Rees-Mogg.
The Royal Mint, which is owned by the government, said it would not comment on how many coins had been made and what would happen to them now, saying this was "commercially sensitive".
But a Treasury spokeswoman said: "We have paused production of the Brexit coin, and will take a final decision in due course."
Since entering Downing Street in July, Boris Johnson has repeatedly promised to get Brexit done by 31 October, describing it as a "do or die" commitment.
But his efforts to do so have been frustrated by Parliament, with MPs voting earlier this week for more time to scrutinise legislation needed to implement his deal with the EU.