Short Answer 
The marginal tax rate applies to the last dollar of income earned and indicates a progressive taxation system, where higher incomes incur higher rates. For Harry and Helen, with a total income of $65,922, their tax liability is $9,169 and after accounting for their total withheld taxes of $9,724, they have a net tax refund of $555.
Step 1: Understanding Marginal Tax Rate
The marginal tax rate is the tax rate applied to the last dollar of income earned. It increases as income rises, indicating a system known as progressive taxation. In this system, those with higher incomes pay a larger percentage in taxes. Key points include:
- Tax rates vary by income brackets.
- Higher income generally leads to higher rates.
- Helps in understanding how much additional income will be taxed.
Step 2: Calculating Tax Liability
Harry and Helen’s total income is $65,922, which places them in the income bracket of $65,900 to $65,950. For this range, the tax liability for a married couple filing jointly is $9,169. Important details for calculating tax are:
- Income bracket: $65,900 – $65,950
- Tax liability amount: $9,169
- Weekly tax withholding: $187
Step 3: Determining Net Tax Refund
The net tax refund of Harry and Helen is derived from subtracting their total withheld taxes from their total tax liability. With a total annual withholding of $9,724 (calculated by $187 x 52 weeks), the formula to find their refund is:
- Total Tax Liability: $9,169
- Total Withheld Amount: $9,724
- Net Tax Refund Calculation: $9,169 – $9,724 = -$555
Thus, their net tax refund is $555.