There is a small difference between “later” and “later on” and that is that “later on” is used when there is a previously arranged agreement to meet. “Later” has a neutral meaning of a time after now.
It is often difficult to see this difference and it is very subtle.
“Later” means at a time that is after another time.
I am going to the cinema later(this means a time after now)
Did you meet John at the cinema? No, I met him later. (this means after going to the cinema)
“Later on” means at a time after another time but the difference is that there is a previously discussed arrangement about what will happen at the later time.
This could be in the form of a meeting.
I’ll see you later on this evening. (there has already been an arrangement to meet)
See you later or See you later on?
“See you later” is used as a way to say goodbye and there usually isn’t a meeting planned.
“See you later on” is also a way to say goodbye but also implies that the two people will be meeting later.
“See you later on” could also be used as a question to confirm that the two people will meet later.
No later than….
You can’t use “later on” when later is a deadline.
You need to hand in your paper no later than Friday.
You need to hand in your paper no later on than Friday.
Later or later on today?
“Later on” is usually used without anything after it but sometimes you can use a time phrase especially if you are confirming a meeting.
What are you doing later today?
Are we meeting later on today?
“Later today” is much more common in English.
Later or later on this week?
“Later this week” is much more common in English. “Later on this week” is only used when there is something previously planned which is happening later in the week.
The event is happening later (on) this week.