The statute of limitations begins to run not from the date of the loan but from the date of the breach of contract ( the nonpayment of the monthly or other term of payment . You would file a formal answer with the Prothonotary of the County in which  the original complaint was filed. Your answer would deny any factual allegations thta you believe to be false. If the statute of limitations has expired before the filing of the original complaint, you would file Preliminary Objections to the Complaint rather than an Answer. The Preliminary Objections would allege the expiration of the applicable statute of limitations. They would be filed with the Prothonotary of the County wherein the original complaint was filed.