Grammatically it's correct, but this is how we apologize for being late. - Sorry I'm late - Sorry for being so late - I'm sorry my response is late

I do not see any grammatical issues with your phrase. However, I read the other comments and I would like to add something. If you are in a formal situation, you may want to consider one of the following, or similar: - I apologize for the delay... - Please excuse the lateness... Using the word "sorry" is appropriate, but it can be too informal for some situations. "Sorry", is good for people you are familiar with and friends. People will know what you mean even if you do not change anything. Please let me know if you need any more help!

It actually is grammatically correct! I had to check the dictionary if lateness was an English word though, because I've almost never heard it used before. I would usually say either "Sorry for being late" or perhaps "Sorry for my tardiness"

Thanks a lot for your help, today I have learned a lot.