TULSA, Oklahoma - If you've filed your state income taxes online in the past, you know filing the state return online will usually cost you.

Many companies offer to file your federal taxes online for free, but now, filing your state returns for free is possible too.  But there is a catch.

In the past, if you filed your federal returns online and then the company you are using charges a small fee to file your state taxes online.

Well, you can get that portion for free, you just have to go through the Oklahoma Tax Commission's web site.

The OTC has a list of five web sites where you can file your state taxes for free.

For TaxSlayer, TurboTax Freedom Edition by Intuit and 1040NOW, you have to have an Adjusted Gross Income, or AGI of around $30,000.

For the other two, you can have an AGI up to $57,000 and still qualify.