So, I'm editing this manuscript of a book that had been previously published by an epub. One of the editors kept changing 'onto' to 'on to' in this manuscript. He was from the U.K. I didn't really understand why he did it, but let it go. But now, I'm running into 'on to' words that I think should be 'onto.' I seem to use it a lot in the phrase 'hold on to' with various forms of 'hold' (held, holding, etc.).
I had to go look it up because it was bugging me. Turns out, the guy from the U.K. was right. It's not considered to be 'standard' in the U.K. to use 'onto' much at all, actually, but is more standard here in the U.S.
So that's the rule? Use 'onto' if you can replace it with 'on' or if you can put 'up' before the onto. Otherwise, use 'on to.'
Here's an example:
I'm going to climb onto my bed.
--I can put the word 'up' before onto. I can also replace 'onto' with on. Either rule can work.
I'm going to hold on to my money.
--'up' and 'on' don't work here.
Cool rule! Now if I can just remember it. LOL!