Workforce.com provides A Few Practical Tips on Responding to a Discrimination Charge. Remember that federal jurisdiction under Title VII begins at 14 employees.
Don’t panic when you receive a discrimination charge. Most people practicing in this area, including the investigators, would agree that the large majority of the charges filed will be found to be "without reasonable cause", meaning that the investigating agency will determine there are insufficient facts to support the allegations.
There is a "Notice of Charge of Discrimination" that accompanies the charge and commonly includes a very short response deadline. You should feel free to promptly request an extension of time for your response when you receive the charge; a 30-day extension is commonly granted.
If you determine that the filing date is more than 300 days from the date of the incident, the charge should be time barred and you should send a letter to the investigator explaining those circumstances. If the agency insists that you are mistaken, you should insist that they explain their position in writing and should include in your response an explanation that the charge is time barred.
Ideally, an investigation should have been conducted at the time the employee complained about being discriminated against by following the employer’s complaint procedure. If that did not happen, upon receipt of the charge it will be necessary that you and your team conduct a prompt, thorough and objective investigation to determine what happened. Doing it right is very important to effectively respond to the charge or to determine whether a settlement should be explored.
Ideally, the person conducting the investigation should not be an attorney. Many courts have ruled that the attorney-client privilege is lost when the attorney puts on the investigator’s hat. Rather, to maintain the privilege, the person making the investigation should report everything to the attorney by correspondence that clearly indicates the information is confidential and attorney-client privileged.
A brief, concise response, on the other hand, will be more favorably received by investigator, will probably be considered more credible and will put you off on the right step. You should keep in mind that unless you can produce credible, persuasive evidence such as witness statements and the comparative information discussed above, the investigating agency will usually believe the complainant’s version of what happened.