While the tax refund is an asset, you should schedule the estimated amount in the case.
Your lawyer will then exempt what they can to protect as much as possible.
In Illinois, you have a $4000 wildcard per debtor to use towards cash, bank accounts, personal household goods and tax refunds. Your Illinois bankruptcy attorney can also exempt the portion attributed to Earned Income Credit.
You will need to file your taxes as soon as possible to work with your lawyer so they can best advise you when is the best time to file your case as well.