The law requires taxpayers to prepay their taxes. Since you do not prepay your taxes through withholding, you may be required to make quarterly estimated tax payments towards your taxes.
To determine if you are required to pay estimated taxes, find the total tax line on your 2007 return. If the amount on line 23 of form 540A, line 37 of form 540 or line 46 of form 540NR is $200 or more ($100 if married filing separately), or if it will be $200 ($100 if married filing separately) or more on your 2008 return, you are required to pay estimated taxes. Use the Estimated Tax Worksheet in the instructions for Form 540ES to figure your estimated tax payments. Use form 540-ES vouchers to pay your estimated tax installments or pay online using our web pay service.