Arrest is not mandatory. If the police has not arrested you so far during the investigation, then at the time of filing charge sheet, generally speaking the police will ask you to be present in court directly at the time of filing / consideration of charge sheet, at which time the court may generally grant you bail. However, this is what is general practice, and there may be some variance from this practice in an individual case.
If you want to get bail before arrest, then you can try anticipatory bail which can be granted by the Sessions Court or the High Court under Section 438 Cr.P.C.
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