It serves no purpose to have a tax assessed but not paid. In some countries the problem of tax arrears has become so critical that governments have taken emergency measures such as tax amnesties and provisions for rescheduling tax payments. These make it easier to collect delinquent taxes, but they can also undermine voluntary compliance if used frequently.
Implementation:
In 1993 the USA Inland Revenue Service ran a massive tax-evader's amnesty programme.