This comes up constantly, usually because a decree was never actually obtained, or because an appeal period had not expired, or because a foreign decree turned out not to be recognised in India.
The civil consequence
Under Section 5(i) read with Section 11 of the Hindu Marriage Act, 1955, neither party may have a living spouse at the time of the marriage. A marriage in breach of that is void, not merely voidable. It is a nullity from the beginning, and either party can obtain a declaration to that effect.
That declaration is obtained by a petition for a decree of nullity in the Family Court, which in Bengaluru means the Family Courts at Nyaya Degula, H. Siddaiah Road, Shanthinagar. Strictly the marriage is void whether or not anybody asks for a decree, but the decree is the document you produce to a bank, an employer, the passport office or a succession court, so it is usually worth having and it is worth obtaining before the witnesses to the first marriage become hard to find. The distinction between void and voidable marriages, and the short and unforgiving limitation periods that attach to the voidable ones, are set out in the guide on annulment of marriage in India.
The criminal consequence
Bigamy is an offence under Section 82 of the Bharatiya Nyaya Sanhita, 2023, which carries forward Section 494 IPC, punishable with imprisonment up to seven years and fine. Where the second marriage was contracted by concealing the first, the punishment is higher, up to ten years. It is a non-cognizable offence and ordinarily requires a complaint by the aggrieved spouse.
That last point governs how the case is actually started. Section 219 of the Bharatiya Nagarik Suraksha Sanhita, 2023 provides that no court shall take cognizance of an offence against marriage under Sections 81 to 84 of the Bharatiya Nyaya Sanhita, which includes bigamy, except on a complaint made by a person aggrieved, with a proviso allowing another person to complain with the leave of the court where the aggrieved person is a child, is of unsound mind, or is unable to appear. So the ordinary route is a private complaint before the jurisdictional Magistrate rather than an FIR at a police station, and a complainant who spends three months trying to get a station to register one has usually lost three months. The guide on bigamy law in India sets out the punishment, the exceptions and what the complaint has to contain.
What actually has to be proved
Bigamy prosecutions fail on proof far more often than on law. The complainant has to prove that the second marriage was in fact solemnised with the ceremonies that make it a marriage. For a Hindu marriage, Section 7 of the Hindu Marriage Act requires the customary rites and ceremonies of either party, and where those include saptapadi the marriage becomes complete and binding when the seventh step is taken. A photograph at a temple, an invitation card, or the couple living together and calling themselves husband and wife, is evidence of a relationship but is not by itself proof that a marriage was solemnised. Bring the witnesses who were present at the ceremony, the priest if you can persuade him, the register if one was kept, and the registration certificate if the second marriage was registered. A certified copy of the marriage register is the strongest single document available in these cases.
A decree of divorce does not take effect for remarriage purposes until the time for appeal has expired, or the appeal has been disposed of. Remarrying the week the decree is pronounced is a real and recurring mistake. Confirm the position with your lawyer before fixing a date. This is Section 15 of the Hindu Marriage Act: it is lawful for either party to marry again when the marriage has been dissolved by a decree and there is no right of appeal, or the time for appealing has expired without an appeal, or an appeal has been presented and dismissed. Under Section 28 of the same Act an appeal has to be preferred within ninety days of the decree, so the safe course is to let that period run and to obtain a no-appeal certificate from the court before the date is fixed.
Where the parties are governed by different personal law
Muslim personal law permits a Muslim man to have more than one wife, subject to its own conditions. That is a genuine difference, but the Supreme Court has held that a Hindu man cannot escape the bigamy provisions by converting to Islam in order to contract a second marriage; the first marriage continues to be governed by the law under which it was solemnised.
The position of the second spouse and the children
The second spouse, if the marriage is void, does not have the status of a legally wedded spouse and the succession consequences are severe. However, Section 16 of the Hindu Marriage Act protects the children of a void or voidable marriage: they are legitimate and inherit from their parents, though their rights in coparcenary property are more limited.
Section 16 says so in terms. A child of a marriage that is null and void under Section 11 is legitimate whether or not a decree of nullity is ever passed and whether or not the marriage is held void otherwise than on a petition under the Act, and a child conceived before a decree annulling a voidable marriage is legitimate too. What the section does not do is give the second spouse any status, and that is where the hardship falls. Whether a woman in a void second marriage can claim permanent alimony has attracted differing views and should not be assumed either way; what is clearer is that she may be able to seek relief under the Protection of Women from Domestic Violence Act, 2005, because that Act is keyed to a domestic relationship rather than to a valid marriage.
Practically, if you are the person who has discovered a subsisting first marriage, do three things before anything else. Obtain a certified copy of the record of the first marriage, whether that is a registration certificate, an entry in a marriage register or the decree that was supposedly passed. Check whether the divorce proceeding said to have ended it was actually filed, and what happened to it, by applying for a copy of the order sheet from the court concerned. And put the discovery in writing, dated, to the other side, because the reply you get is frequently the most useful document in the case.