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Got a “personal” bonus from my boss. Do I have to pay taxes and if so, how do I go about that?
As others have mentioned yes it is taxable. Whether it goes through payroll and has FICA taken out is your issue in terms that you need to report it and you will an extra 7.5% self employment taxes that would normally be covered by your employer. Your employer may have problems but that isn't your issue.  Contrary to what other users are saying chances are there won't be any penalties for you. Best case you have already paid 100% of last years tax liability and you can file your normal tax return with no issues.  Worst case you need to pay quarterly taxes on that amount in the current quarter. IRS quarters are a little weird but I think you need to pay by Jan 15th for a December payment. You don't have to calculate your entire liability you can just fill out the very short form and attach a check for about what you will owe. There is a form you can fill out to show what quarter you received the money and you paid in it is a bit more complex but will avoid the penalty. For penalties quarterly taxes count in the quarter received where as payroll deductions count as if they were paid in the first quarter of the year. From the IRS The United States income tax is a pay-as-you-go tax, which means that tax must be paid as you earn or receive your income during the year. You can either do this through withholding or by making estimated tax payments. If you do not pay your tax through withholding, or do not pay enough tax that way, you might also have to pay estimated taxes. If you did not pay enough tax throughout the year, either through withholding or by making estimated tax payments, you may have to pay a penalty for underpayment of estimated tax. Generally, most taxpayers will avoid this penalty if they owe less than $1,000 in tax after subtracting their withholdings and credits, or if they paid at least 90% of the tax for the current year, or 100% of the tax shown on the return for the prior year, whichever is smaller.