You can choose to have income tax withheld from unemployment compensation. To make this choice, you will have to fill out Form W-4V (or a similar form provided by the payer) and give it to the payer.
The first $2,400 of unemployment compensation is excluded from income. All other unemployment compensation is taxable. So, if you do not have income tax withheld, you may have to pay estimated tax. See chapter 2.
If you do not pay enough tax, either through withholding or estimated tax, or a combination of both, you may have to pay a penalty. See chapter 4.taxmap/pubs/p505-007.htm#en_us_publink10007304
If you receive $10 or more in unemployment compensation, you will receive a Form 1099-G, Certain Government Payments. Box 1 will show the amount of unemployment compensation you got for the year. Box 4 will show the amount of federal income tax withheld, if any.