401(k) plans are deferred income plans, meaning the tax is deferred until it is taken out. For federal purposes, you will have to include in your income whatever you take from the plan that year. If you take the whole $24,000, you will have to add $24,000 to your taxable income on your 1040 (line 16b). The amount of tax this will trigger depends completely on many, many other things such as your other taxable income, whether you are married, the number of dependents you have, etc. It could be as high as 35% or as low as 0%. Neither are likely, but I wanted to give you the extreems.

If you are not working, single, dependent on someone else (live with your mother), and have no income or deductions, then your federal income tax on the $24,000 will be around $2,750.

You may owe state income tax too. If you do, chances are it will be substantially less than the $2,750. Some states don’t tax this type of income.

As far as inheritance tax, the IRS has none. Instead, they have estate tax which your father’s estate will have to pay. It is extremely unlikely that his estate is large enough to trigger an estate tax.

Some states have inheritance taxes. Most don’t tax IRA or 401(k) inheritance. Even if they did, it probably wouldn’t be much.

Good luck!