Yes and no. Yes, they can sue you at any time. Anyone can sue anyone else at any time if they pay a filing fee and file a complaint.

No, they shouldn't sue you after the statute of limitations has expired. To do so is a violation of the FDCPA. By entering proper defenses, you will prevail, and, you may have a claim against them.

Some states (like North Carolina where I live) have laws which actually preclude a creditor from suing after the statute of limitations has run. To my knowledge, Pennsylvania does not have such a law yet. You and your fellow Pennsylvanians need to lobby your legislature to pass this protection.

The statute of limitations is a waivable defense that only applies to lawsuits. What that means is that if you ignore the lawsuit and don't file an answer, the defense is waived and the debt collector may get a judgment.

So if you are sued by a debt collector or junk debt buyer or even an original creditor 4 or more years after the debt became delinquent (assuming that the debt was incurred in Pennsylvania), then you need to go immediately to a lawyer. I know attorney Greg Artim here at Law Guru does statewide credit card defense and I am sure there are others in the Philadelphia area as well. You have a very short time (20 days) after you receive the complaint, so don't delay.

Pennsylvania has a law modeled after the Fair Debt Collections Practices Act called the Pennsylvania Fair Credit Extension Uniformity Act. It applies to debt collectors as well as original creditors and sets forth the penalties for those violating the act.

Some debt collectors and others know the laws and will not risk a lawsuit. Instead, they will keep calling and try to collect. If you are contacted, then you need to write, not call them, and send what I term as a "drop dead" letter. Essentially, it tells the collector to "drop dead" as the debt is past the statute of limitations and not to bother you anymore. There are dozens of free "drop dead" letters on the internet. However, I don't recommend that you do this on your own as you want to be careful so as not revive the statute of limitations.

Under no circumstances should you pay them a penny if you think that the statute of limitations has expired. Partial payment of any kind will revive the statute. However, just because the statute of limitations has run does not mean that the debt goes away or that it cannot be on your credit report. There may be valid reasons to resolve the debt even though the statute has run. You should only do this, if you are interested, after consulting with an attorney because you do not want to run the risk of reviving the debt.