While media outlets have projected that Mr Biden won the election, the results are not official until either Mr Trump concedes or all vote counts are certified and electors officially choose the next president.
The president is unlikely to concede any time soon as he wages multiple legal battles contesting results in key states that decided the election for Mr Biden.
As a result, the balance hangs in the balance. One website alone, Betfair Exchange, has almost $600m (£455.5m) in bookings awaiting an official result, more than double its $258m (£195m) in 2016.
“We will only settle the markets when there is certainty around which candidate has the most projected Electoral College votes,” Betfair said in its latest market settlement update.
“Before settling the markets, we must therefore wait for clarity around ongoing vote counts, recounts and any potential legal challenges to the results.”
One Betfair punter is hoping more than most those legal challenges fail, having placed a $1.32m (£1m) bet on Mr Biden that would pay out