I believe the tax lien was in the transaction period when the closing agency was doing the title search.
The house was bank-own. It was on market a year ago and I viewed it but it was withdrawn from market due to title issue. It was put back on market a year later and I viewed it immediately and made an offer higher than the asking price.
Obviously, the title search did not do a good job.
It was a long story to get the house I have been happily lived in for 9 years now. :)