Technically there is not, but a motion to reopen your case must be filed with the Court and the motion is subject to approval by the Bankruptcy Judge assigned your case (assuming the Judge is still sitting). The granting of the motion my turn on the reason that you seek to reopen the case. As a rule of thumb, it should be possible to reopen the case if it has been a year or less since the case was closed. If you are seeking to reopen the case because of an omitted creditor and yours was a "no asset" case, there is applicable case law that might make the necessity of reopening the case moot.
There is no time limit to reopen.
If the case is closed, you have to reopen, as described by my colleague.
If the case is still open, after a discharge, you can amend until the court closes it.
In my districts, most cases remain open after discharge, usually for a few weeks.
General legal advice is offered for educational purposes only. A consultation with a qualified attorney is required to determine specific legal advice as to your situation and applicable law. We are a debt relief agency and we help people file for relief under the bankruptcy laws.
First you have to consider why you would need to amend. Is it to add a creditor, or to include an asset or lawsuit claim you forgot to list or mention? In New Jersey and elsewhere in the Third Circuit, if your case was a "no asset" case, meaning the trustee did not find anything to generate money for creditors, your discharge covers all creditors that could have been listed but were not. If your purpose is to get a discharge of some otherwise dischargeable claim that was not listed, reopening may not be necessary. If on the other hand you need to list an asset that was not included, reopening may be far more important. If you move to reopen you will have to pay another filing fee. I would recommend consulting with a qualified bankruptcy lawyer about what you need to do, as there are some issues and considerations that might make it worthwhile for you to reopen. Most times, however, it is not needed simply to add creditors you missed.
The foregoing answer is for informational and educational purposes, not for purposes of legal representation. This answer is based on New Jersey law and is necessarily general in nature.. Laws in other states may be different, and each situation is different, so this answer might not apply accurately to you. No attorney client relationship is to be implied from this answer. Always seek independent legal advice.