How long does unpaid tax liens remain on credit report?

Indefinitely. :(

I fully agree with the both of them, but there is a way to make tax liens disappear from your credit reports completely.
In 2011 and 2012, the IRS implemented the “Fresh Start” initiative, which includes a policy that allows certain taxpayers to request that their tax liens be withdrawn, even before the tax debt has been paid.

Unfortunately, as per the federal law, unpaid tax liens should remain on the credit report forever. However, the credit bureaus can remove them after a long time.

But once the tax lien is paid and released, it must be removed seven years from the date the tax lien was filed.

Yes, there are certain criteria if you want to qualify and request your lien be withdrawn.

1. Your tax liability has been satisfied (you’ve paid what you owe) and your lien has been released;
2. You are in compliance for the past three years in filing your individual and business returns, and information returns (as applicable) and;
3. You are current on your estimated tax payments and federal tax deposits, as applicable.