High taxes on year-end bonus checks can be attributed to several factors. Firstly, these bonus payments are often viewed as additional income and are thus subject to regular income tax rates. Secondly, the lump sum nature of these bonuses can push individuals into higher tax brackets, resulting in a higher tax liability. Moreover, certain deductions and exemptions that may be applicable throughout the year may not apply to these bonuses, further contributing to the higher tax amount. Lastly, some jurisdictions impose additional levies on bonuses, such as social security contributions or Medicare taxes. Understanding these reasons can help individuals plan their finances accordingly and mitigate the impact of high taxes on their year-end bonus checks.