Filing a Michigan state extension allows you to have additional time to complete your state tax form while keeping you in compliance with the state tax code. If you simply file your return late, you will be assessed late filing penalties and compound interest on your outstanding balance. Receiving a state tax extension will help you to avoid these charges. Keep in mind, however, that you can only receive an extension in Michigan if you have good cause for not submitting your return on time.http://www.michigan.gov/documents/4_144975_7.pdf 

The initial filing deadline to submit a 2010 Michigan state tax return is April 18, 2011, the same day that your federal tax return is due.http://www.michigan.gov/wps/wcm/connect/f4f50680456dae8692cfd6ef076fdefc/MI1040book_341323_7.pdf?MOD=AJPERES&CONVERT_TO=url   If you receive an extension you will have an additional six months to file your return, extending your filing deadline to October 18. It is important to note that an approved extension does not apply to the due date for any payment due. If you owe additional tax, you must still remit your entire balance by April 15 to avoid late penalties and interest charges.http://www.michigan.gov/wps/wcm/connect/85e7fc00403c9672957eb5d5c1d1ac50/4_144975_7.pdf?MOD=AJPERES&CONVERT_TO=url 

Before you begin preparing your extension, you should collect all of the information you will need to calculate your tax liability. The information you will use is the same data you need to prepare your tax return, so be sure to keep it in one place so you can use it later:

1. The total amount of your earned income––If you are an employee, this will be reported on your Form W-2 or Form 1099 as your total taxable wages. If you are self-employed, you must total your gross earnings and then subtract any applicable business deductions you can claim.
2. The total unearned income you received that is subject to Michigan taxation––Most sources of unearned income, such as unemployment compensation, lottery winnings, and bank interest are taxable in Michigan.
3. The amount of state income taxes you have already paid in during the year––For employees, this will be shown on Form W-2 as state taxes withheld. Self-employed individuals will use the total of any estimated tax payments made.
4. A copy of your completed federal income tax return, if you are filing one at this time
   

You will use your federal adjusted gross income to begin calculating your state tax liability on the Michigan tax return, so complete your federal return before you get started on your state extension. If you will also be requesting a federal tax extension, you may want to consult a tax professional to help you arrive at this figure.http://www.michigan.gov/documents/4_144975_7.pdf  

If you need to complete the Michigan extension request, you will also need the following:

1. Your Social Security number
2. Your complete mailing address
3. Your spouse's full name and Social Security number, if you are filing a joint tax returnhttp://www.michigan.gov/documents/4_144975_7.pdf 

Your next step is to assess the amount of additional state taxes you will owe, if any. To do this, you need to obtain a paper copy of Form MI-1040 "Michigan Individual Income Tax Return" and the form instruction booklet. If you have Internet access, you can download these forms from the Michigan Department of Treasury website. You can also obtain a paper copy of these documents from your public library.http://www.michigan.gov/documents/taxes/MI-1040_341136_7.pdf 

Be sure to read the tax form instructions in their entirety before proceeding. The booklet provides an explanation of income adjustments you may need to make and state tax credits you might qualify to use on your return. If you get confused by any part of the form, stop and consult the instructions.http://www.michigan.gov/documents/taxes/MI1040book_341323_7.pdf 

Begin the form by transferring the amount of your federal adjusted gross income from your IRS Form 1040 to line 1 of the Michigan form. Then separate the total of your earned income and enter that on line 1a. In the next two sections of the form, you will make additions and subtractions to account for income received that is taxable to Michigan but not taxable to the federal government and vice versa. On line 10, you will arrive at your Michigan adjusted gross income.http://www.michigan.gov/documents/taxes/MI-1040_341136_7.pdf 

Subtract your standard or itemized deductions to see the total of your Michigan taxable income. Consult the tax table to find the amount of tax owed on your income and enter that as your income tax on line 19. This is the total of your tax liability. Then deduct any state tax credits you are eligible to claim and add any local taxes you will also owe.http://www.michigan.gov/documents/taxes/MI-1040_341136_7.pdf 

Deduct the amount of your state income taxes already paid through withholding or estimated tax payments. What remains after this will either be an overpayment entitling you to a refund or an underpayment requiring you to pay an additional balance due.http://www.michigan.gov/documents/taxes/MI-1040_341136_7.pdf 

If you calculate that you will receive a refund, you can skip this step. Simply prepare your return when you are able and you should be able to receive the full amount of your refund from the Department of Treasury. If you have received a federal tax extension, you will need to send in a copy of your completed Form 4868 as well as the amount of your payment due before April 18. Doing so will automatically grant you a Michigan extension with your federal extension.http://www.irs.gov/file/article/0,,id=105061,00.html 

If you will only be requesting a Michigan tax extension, you will need to complete Form 4 "Application for Extension of Time to File Michigan Tax Returns". This form can also be downloaded from the Michigan Department of Treasury website or obtained from your local library.http://www.michigan.gov/documents/4_144975_7.pdf 

Complete the form by entering your full name and Social Security number as well as your spouse's if applicable. Then enter your mailing address and select the type of tax return you will eventually file. Write in the amount of the tax payment you are making and then make a copy of the completed form. Send the form, along with a check or money order for your balance, to the address listed on the voucher.http://www.michigan.gov/documents/4_144975_7.pdf 

If you are unable to pay your entire tax balance, send in what you can and contact the Michigan Department of Treasury about setting up a payment plan. Once you remit payment, begin working on your state return as soon as possible.