Estimated tax is the method used to pay tax on income that is not subject to withholding. This includes income from self-employment, interest, dividends, alimony, rent, gains from the sale of assets, prizes, and awards. You also may have to pay estimated tax if the amount of income tax being withheld from your salary, pension, or other income is not enough.
Estimated tax is used to pay both income tax and self-employment tax, as well as other taxes and amounts reported on your tax return. 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. If you do not pay enough by the due date of each payment period (see When To Pay Estimated Tax on page 22), you may be charged a penalty even if you are due a refund when you file your tax return. For information on when the penalty applies, see chapter 4.
Form needed: Payment Voucher from form 1040-ES
Each payment of estimated tax by check or money order must be accompanied by a payment voucher from Form 1040-ES. If you made estimated tax payments last year and did not use a paid preparer to file your return, you should receive a copy of the 2011 Form 1040-ES in the mail. It will have payment vouchers preprinted with your name, address, and social security number. Using the preprinted vouchers will speed processing, reduce the chance of error, and help save processing costs.
Use the window envelopes that came with your Form 1040-ES package. If you use your own envelopes, make sure you mail your payment vouchers to the address shown in the Form 1040-ES instructions for the place where you live
Link to download Pymt Coucher for 2011: