There is no evidence of widespread voter fraud in the 2020 elections and president-election Joe Biden and his party has not forfeited the election.
Trump's claims have ranged from 'more people voted than the number of people registered in a state,' and 'the dominion system deleted 2.7 million votes for President Trump nationwide' and many more. Still, claims around voter fraud made by him have been repeatedly debunked. No credible media organization has found widespread evidence of voter fraud. Trump and his aides have presented no actual evidence of "illegal" votes at all. The Trump campaign has also filed lawsuits in some key states, including Pennsylvania and Georgia. However, in many cases, the campaign is dropping lawsuits, or the court has dismissed their lawsuits.
President-elect Joe Biden has not forfeited the election and is set to take an oath on Jan 20, 2021.