Which box on the W-2 lists other compensations or reductions applicable to taxable income?

Box 12 on the W-2 is designated for reporting various forms of compensation and deductions that may not fall into the standard income categories. This box can include important information such as contributions to 401(k) plans, adoption assistance, and other specific deductions that can affect the taxpayer's taxable income. The details provided in this section are crucial for individuals who need to report additional income or deductions when filing their tax returns.

While Box 1 contains the total taxable wages, which include wages, tips, and other compensation, it does not break out specific items or various deductions. Box 3 reports Medicare wages, which can also be different from the amount reported in Box 1, due to pre-tax deductions, but it doesn't provide the detailed breakdown. Box 15 relates to state tax information, which is important but not directly relevant to other compensations or reductions applicable to taxable income. Therefore, Box 12 is specifically designed for that purpose, making it the correct answer.