We may not know who won the presidential race on November 3rd, and that’s normal.
In modern elections, no state reports certified election results on Election Day. Provisional ballots, military ballots from overseas, and ballots that are accepted with an Election Day postmark can be counted days after voting ends. State laws give election officials weeks to finalize results to ensure ALL votes are completely and accurately counted. News outlets may call winners in advance of certified results, but those are based on projections using statistical models and partial counts.
This year in particular, it may take longer to finalize results due to the historic number of voters using mail ballots. Processing those votes takes time and specialized equipment, and some states aren’t able to begin processing ballots until Election Day. But even in those cases, election officials are committed to properly and completely counting ballots – even if it takes a little extra time.
For context, here is a chart of the percent of votes counted in 2016 the day after Election Day (source: Charles Stewart III).