I find some properties do email a preliminary folio (receipt) the night before (well really very early the morning of departure). I get a second final folio from them when I checkout. Haven't been able to figure out a pattern for which properties are doing the preliminary folios. Speculation, it may be dependent on the PMS system they are using.

For email receipts, you should get them real time. When I ask for one, I check while I am still at the front desk. I mainly only do this at properties where I didn't receive a preliminary folio. If I don't get the email receipt within a minute or so, I also asked for a printed receipt.

As ​​​jayer already noted, sometimes folks are in a hurry when leaving and don't have time to do a checkout at the desk. Murphy's law of hotel stays, inevitably those are the times the email folio doesn't get sent.

TL;DR most properties I get the email receipt in a timely fashion without an issue. When requesting an email receipt at the front desk, it should almost instantly arrive in your email inbox. If not, ask for a printed receipt as a backup.

--Jon