Looking on the internet deeply has found these results:

I should have informed you earlier is the most popular phrase on the web.

I should have been informed you earlier 10 results on the web	I should have informed you earlier 112 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	I should have informed you earlier, but I have already started a discussion on the forums on this matter. If you agree with this change we can hear what the other ... I should have informed you earlier before I subscribe to your suggestions. After few investigations, I came to know that we can't send any ... Dec 23, 2014 ... The boss is very apologetic too and says, 'I am sorry, I should have informed you earlier. But I assumed that you spoke to my secretary and she ... ... (strategic alliance). Dear Dr. Jones, I should have informed you earlier that we have taken over responsibility for the XYZ Project from Dr. Chen as of last May.

I should have been informed you earlier

10 results on the web

I should have informed you earlier

112 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

I should have informed you earlier, but I have already started a discussion on the forums on this matter. If you agree with this change we can hear what the other ...
I should have informed you earlier before I subscribe to your suggestions. After few investigations, I came to know that we can't send any ...
Dec 23, 2014 ... The boss is very apologetic too and says, 'I am sorry, I should have informed you earlier. But I assumed that you spoke to my secretary and she ...
... (strategic alliance). Dear Dr. Jones, I should have informed you earlier that we have taken over responsibility for the XYZ Project from Dr. Chen as of last May.