using unique identifiers while performing function

Hello I need some help:

I have a spread sheet with dozens of thousands of unique identifies (Subscriber IDs). Each one represents a person.

Some people were billed for a coverage periods and some people's billing for a coverage period was skipped.

Now I have to figure out which people need to be billed for the because previous coverage periods were not billed, according to the current months record (July).

EXAMPLE:

https://lh3.googleusercontent.com/-7...or%2Bclint.PNG
NOTE:
Red shows the discrepancy that a person needs to be billed for
Green represents the journal entry and billing coverage period accounting for each other and not bill needs to be issued.

ADRI's coverage period from 2/1 - 2/29 was billed in June.

June's bill that covered 2/1 - 2/29 coverage period has a July journal entry for said coverage period.

However, the coverage period from 1/1 - 1/31, has a July journal entry, but no 1/1 - 1/31 billing month.

Therefore, ADRI, needs to be billed for coverage period, the 1/1-131.