How much does late Recommendation Letter affect my application?

[bcjw5]

Hi All,
Just a quick question regarding the LOR. Most of the Physics PhD programs that I've applied require 3 recommendation letters. Two of my professors have already submitted the LORs long time ago (Big Thanks!!!! ), but the 3rd professor has really been procrastinating... Some of the programs I've applied have a deadline by January 15th, and now it's already early February, and he still didn't submit the 3rd LOR despite my repeated reminders. I've reminded him again three days ago and he promised to submit it as soon as possible. But even if he submits it this week, it's already three weeks past the deadline... Well, I'm wondering how much would a (extremely) late LOR affect my application? Is sending an apology email to each school's Admission Office would be of any help?
(Note: I think the 3rd professor's missing LOR is probably the least important among the three LORs. I've only worked with him as a TA teaching Intermediate Classical Mechanics for one semester. The other two professors' LORs are about a continuous two-year biophysics research and a nine-month nuclear physics project.)
Thanks a lot for anyone who have read through my post!

[JellyJam]

It is hard to say. Truly, it is up to the individual program to make a decision on the importance of a missing piece of information. Most likely, if the program is greatly interested in your application, they will contact you to ask precisely what is going on with the missing LoR. On the other hand, if your application did not interest the admissions committee from the start, it is unlikely that the missing LoR would have greatly swayed their opinion.

An example from my own experience: I had incorrectly uploaded my statement of purpose and my diversity essay for the physics program at UCSB. Late January, they called me up to ask exactly what was going on with the said documents. Of course, when I received the call, I was horribly embarrassed by the mistake, and remedied it that same day. In the following weeks, I had thought that my application would henceforth be rejected because of the mistake. However, to my surprise, I was admitted.

In conclusion, a missing or late LoR doesn't necessarily mean your application will be ignored or rejected. However, it certainly doesn't help your chances of being admitted. In the end, it may be of value for you to email or contact your programs to explain the situation, and apologize the delay.