Determining the Date of Birth (DOB) for a Hindu Undivided Family (HUF) has two key aspects. Under traditional Hindu Law, an HUF comes into existence upon marriage. However, for income tax purposes, the DOB of an HUF can be established by the date of a registered HUF deed.
As per Hindu Law, HUF comes into existence once you are married. But under income tax you can create a huf deed and date of this deed can be the birth of HUF.