[Idiom] Not that I know (of).

[beachboy]

https://www.ldoceonline.com/dictionary/not-that-i-know-of

- Did he call earlier?
- Not that I know of.

Is it ever grammatical to say Not that I know (dropping the of) when answering any question?

 

[emsr2d2]

No, the "of" is required. You can also say "Not as far as I know".

 

[tedmc]

Not that I know of is a set phrase in spoken English, though I don't think it is wrong to drop the off (since not as far as I know is okay)

 

[emsr2d2]

Not that I know of is a set phrase in [STRIKE]spoken[/STRIKE] English, though I don't think it is wrong to drop the [STRIKE]off[/STRIKE] of (since not as far as I know is okay).

Note my corrections above. As I said in post #2, it is wrong to omit the "of" in "Not that I know of".