They can legally pursue 7 year from the date of the LAST CHARGE OR PAYMENT ACTIVITY. Fair Debt Collection Practices Act and the statute of limitation governs how this is collected.

Hypothetically, if this bill was pending with insurance and final payments and and processing was completed on pending charges, they they would bill you for the remaining amount (and 18 months would be not unusual, I worked in medical billing you would be amazed how long it can take). The bill can be pursued up to 7 years from the date of the last payment by the insurance company.

They will send it out to collection usually in 90 to 120 days. The insurance company can put this on your credit profile as a bad debt. The law is changing on the ability to medical debt to your credit profile but this would likely be grandfathered in because it was over a year ago.

IF you can afford to try to settle with the hospital. We routinely settled for 50% to 75% for balances after insurance if people could come up with the lump sum within 30 days. IF you go this route get the settlement agreement in writing (an email is sufficient, a letter is better). If not you can always make small monthly payments for how ever long it takes to pay it off.

i will you luck and if it is any consolation, this happens all the time, especially with insurance processing. With one insurance company we had to submit a claim 3 times before the company would process the the claim and they would routinely take 9 month to a year to pay the bill. It was 2 years later before the patient even saw the balance after insurance.