The treatment of unsecured tax penalties in bankruptcy is linked to the dischargeability of the tax to which they are related. Penalties associated with taxes arising more than three years before the bankruptcy are dischargeable, even if the tax to which it is linked isn't dischargeable.
All unsecured penalties are dischargeable.
Penalties can be paid at the same rate as non tax claims, usually a fraction on the dollar. No new penalties accrue on prepetition taxes during the Chapter 13 payment plan. If a tax lien attaches to actual equity in assets, under the current law, the penalties are secured as well as the tax, even if they would be dischargeable if not secured.