Query goofed up!

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I have a query that needs to get all the employee records that have not made
a cobra insurance payment within a specified month. Each employee should be
in the General Cobra db (primary) which is joined by ss# to the Payments db.
I'm trying to match the ss# in each database and then see if they made a pmt
in the month in question. My SQL isn't right and I don't have a lot of
experience with this. I'd really appreciate help with this. Thanks! Please
try not to laugh too much at this:

SELECT [General Cobra Information].[SocialSecurity#], [General Cobra
Information].[First Name], [General Cobra Information].[Last Name]
FROM [General Cobra Information] LEFT JOIN Payment ON [General Cobra
Information].[SocialSecurity#] = Payment.[SocialSecurity#]
WHERE (([Payment].[Month] = [What month?] AND (Payment.[SocialSecurity#]) Is
Null));

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