The deadline for claiming the two £1 million prizes expired at 11pm yesterday, more than 180 days after the EuroMillions draw on July 26.
One of the winning tickets was bought in Fife and the other in East Dunbartonshire.
The money, plus the interest it earned, has now passed over to the National Lottery Good Causes.
Earlier this week it emerged that another winner from Fife had also failed to collect the lottery prize that would have made them a millionaire.
They bought the EuroMillions Millionaire Raffle ticket in Fife on July 23 and the prize was passed to the National Lottery Good Causes after it remained unclaimed for more than 180 days.
A National Lottery spokesman said: "To avoid this unfortunate situation happening again, I would urge all National Lottery players to check their tickets on a regular basis.
"We tried very hard to find the ticket-holder and it's a real shame that they have missed out, but there is still one winner - the nation. This money, and all the interest earned over the 180 days, will now go to benefit projects all over the UK funded by The National Lottery."
The unclaimed prizes will be added to the £31 billion that has already been raised by National Lottery players since 1994 to help more than 420,000 projects across the arts, sports, heritage, charities, health, education and the environment.