I need a criminal background check in which I have to pay for the fingerprints. I've had a fingerprint background check done in march this year through the fbi, it is now December do I have to pay to again for my fingerprints to be sent to the fbi, or do they already have them.

They have them on file, but they probably do not keep your request on file. So you will need to resubmit a sample for them to check. Don't you have a copy of the results from March? Isn't that enough?

You might try just sending them a copy of the March report and see if they can update it. Contact your local FBI office and ask.

The only fingerprints the FBI retains are those submitted for criminal offenses. That's the database that your (new) fingerprints are compared to when they are submitted. If your prints were submitted in March and returned as "No Hit/No Record Found" then those prints are not retained.
I'm assuming this is for employment purposes,so whether "new" prints need to be submitted depends on several different criteria such as, who the emnployer is, whetehr or not it's the same employer, whether you have been unemployed for 90 days since March, etc.
If the fingerprinteing is state mandated- i.e. job as a teacher or a health care worker, you may be able to request your former employer or the state provide you with the results (depending on what state is involved).
On the other hand, if it's for a bank, chances are you'll just have to have it done again. Your best bet is to talk to your employer.

The US government maintains a database of fingerprints, not only of criminals. Military, Government employees, people getting security clearances etc are all kept on file. But they don't keep a record of requests.

The FBI and the Homeland Defense, both have a wide fingerprint collection. They have criminal fingerprint, and fingerprints for anyone who has had a fingerprint check ran, for employment, for gun permits, for background searches.

The FBI and Homeland Defense, have more non criminal fingerprints than criminal.

The criminal records is another report, and the actual criminal recored is not stored with the fignerprint, the fingerprint merely tells ID, what ID you used the last time you were fingerprinted, for comparison. Then the ID that comes back to that fingerprint is matched to the NCIC records in the US, for the criminal history if any.

The fee you pay for a fingerprint check, is not a one time fee, it is the fee
1. for the agency who is taking your prints, ( sometimes private companies, sometimes police depatment)
2. for the processing of the fingerprint check
3. for the cross reference of the NCIC report.

You pay this fee every time you are fingerprinted for a check ( or someone pays it) with the exception of when you are arrested, and that is not charged for ( at least yet)