The National Assembly Budget Office(NABO) has supported the Members and committees of the National Assembly by conducting cost estimates for enacting or revising bills among many other tasks since its establishment. Revenue & Tax Analysis Team in NABO has provided cost estimates for tax bills affecting tax revenues on the requests of the Members or committees of the National Assembly. It aims at showing how enactment or revision of a tax bill would change tax revenues over the next five years or less.

NABO has been requested a total of 175 cases of tax bill cost estimates in 2008. "Cases of Cost Estimates for Tax Bills in 2008", the fourth case study, has been extracted adequate cases from those cost estimates of tax bill in 2008. This is composed of two parts. The first part introduces brief history and presents conditions of tax bill cost estimates, and analyses the cost estimates from various viewpoints. Then 24 most important cases are categorized into tax laws in the second part.