The cases are accompanied by an explanation of the reasons for the different results between current tax law (2006) and the proposed SITP and GITP.
Under both the SITP and the GITP, the income tax before credits is $6,291 because the standard deduction and the deduction for personal and dependency exemptions have been replaced by a Family Credit.
At this income level, the marginal tax rates of the SITP and the GITP are both 15%.
Nevertheless, the SITP and the GITP are more beneficial to taxpayers with ordinary income up to $60,000, as the proposed Family Credit covers the income tax on a greater amount of taxable income than the Child Tax Credit, and is available on all dependent children, without an age cap.
In Case 2, in the current, SITP, and GITP scenarios the net income tax after credits is almost the same.
In Case 3, all of the couple's itemized deductions and personal exemptions are lost under SITP and GITP and replaced by a $3,300 Family Credit and a $1,703 Home Credit (15% of the mortgage interest).
Even the addition of two children would not change the comparison between the current system and the proposed SITP or GITP.
Case 4 illustrates the effects of the different treatment of interest income under SITP and GITP.
While SITP taxes interest income at the regular tax rates, GITP taxes interest income at a maximum 15% rate.
Case 5 illustrates the effects of the elimination of the alternative minimum tax (AMT) under SITP and GITP.
The loss of the itemized and personal exemption deductions under the proposed plans would increase the initial income tax under both SITP and GITP to more than under the current law, even with the AMT.