I already have my SAT (1570), 2 subject test scores (800+800) and my Harvard RD application ready to submit. But, I am taking 2 more subject tests in December the results for which I will obtain around 20 Dec.
Should I wait until I get the extra subject tests results? I want to make my application as competitive as possible.
Thanks for your advice.
First off, SAT Subject Tests are optional at Harvard – meaning they are not required.
Secondly, when submitting SAT Subject Tests, Harvard only requires two of them. As you already have scored a perfect score on two SAT Subject Tests, submitting more SAT Subject Test Scores (even if they also are perfect scores) WILL NOT increase your chances of acceptance. In fact, if your high school’s policy does not specifically require you to take SAT Subject Tests, it might make you seem a bit test obsessed – not a good thing in the Admissions world. So, IMHO, you should cancel the two SAT Subject Tests you have scheduled in December and submit your RD application when you feel your essays are ready.
Do your additional two subject tests reveal any interesting or different skills that the rest of your application does not already highlight? For instance, are you a very STEM-oriented person and so is most of your application, and your additional tests will be high scores in Literature or humanities subjects, showing a diverse candidate? Did you do poorly in math on your SAT and transcript but your additional subject test in Math II will be a high score? Did you write your application about your love for History and your additional subject tests will corroborate that? If so, they might be marginally valuable. Ask yourself whether taking those extra tests will help you tell the story you want to convey to the admissions office. If not, don’t bother. In the majority of cases, it most likely won’t really matter. Feel free to do whatever gives you peace of mind.
@gibby is totally correct. I will also say that at Harvard, little elves in the basement (well, work/study students) assemble a cover sheet which lists only the top 2 Subject Test scores; the other scores will appear further inside the package if the AO decides to dig for them. So additional scores will really not benefit you, and as gibby says, might raise an eyebrow. I would think your time would be better spent elsewhere. But do it if it makes you feel better. Good luck.
Thanks for the advice!
In fact, I should have mentioned that I want to major in either Physics or Computer Science. The 2 subject tests I have already taken are Math level 2 and Physics. The two I am going to take are Chemistry and French.
I am going to do the December tests anyways because I need them for other universities. I will think more about sending the extra scores to Harvard - will also talk to my GC.
The two scores you have already are good fits for your application and intended major. I can’t imagine any school requiring four subject tests. If you like taking tests recreationally, have fun, but it doesn’t seem necessary unless one of your top choices wants four tests 
None do in the US. Georgetown recommends 3.
While the additional tests pointless from an admissions perspective, as I said above, a high enough score on French would at least get you out of the foreign language requirement, assuming you have not fulfilled that some other way. Good luck.
I am applying to Indian universities which require 3. as I was going to the testing centre do 1 more anyway, I thought why not 2