Often times when someone files for bankruptcy, they do still have some money in their bank account. However, as soon as you file your case, an estate is created that contains everything you own. What this means is that you will no longer be in control over your assets for a period of time, typically 3 months during a standard Chapter 7 bankruptcy case. However, much of your assets, including money in your checking or savings accounts is protected and can be used by you if properly claimed as exempt from the bankruptcy estate.
After you file your bankruptcy case, there will be a person called a Trustee who is responsible for administering the estate. This Trustee is tasked with liquidating any assets you have which cannot be protected by the bankruptcy code, See 11 U.S.C. § 522(D). With this said, you do have a duty to disclose how much money you have in financial institutions on your personal property schedule (schedule B). Once you do this, depending upon the state which you are filing and what exemptions are available to you, and whether you have any equity in your home, you may be able to protect up to and use as much as $11,975.00. However, in other situations, you can only protect a very limited amount, depending upon what other assets you have and if you need to use part of your exemptions to protect them, such as a tax refund, equity in a vehicle or other such things.
As with most things in the law, every case is extremely fact specific and unique. To that end, you will want to consult with an experienced bankruptcy attorney who can advise you on whether or not you can exempt and use funds in your bank.