Short answer
Yes. A nikah with offer and acceptance before two witnesses is valid in the sharia even if it is never registered with the state. But scholars strongly advise registering it, because without legal recognition a wife and children can lose their rights to support, inheritance and protection. Where the law requires registration, follow it.
Registration is not a condition of a valid nikah. It is an important way of protecting rights and announcing the marriage, and Muslims are expected to keep lawful state requirements in permissible matters, so leaving it without good reason is blameworthy.
The four schools agree on this.
Explanation
In many countries a nikah and a legal marriage are two separate events. In the UK, for example, a nikah in a mosque is often not a legal marriage on its own. Many couples do the nikah first and register later, and some never register at all.
Is it valid? The conditions of a nikah are set out in conditions of a valid nikah, and the four schools agree that state registration is not one of them, though three schools also require the wali. A couple with a valid nikah are married before Allah, their children are legitimate, and mahr, maintenance, iddah and inheritance apply between them in the sharia.
Why register anyway. Allah commanded that even a debt be written down (2:282). A marriage, with its mahr and lifelong rights, deserves at least the same care.
- The wife's protection. If the marriage breaks down, an unregistered wife may have no legal claim to the home, maintenance or shared assets.
- Inheritance. The state may not treat her as his heir.
- Children. Birth records, citizenship and custody can become harder.
- Divorce. Without registration, only an Islamic council can help in a dispute, and there is no court to enforce its decision.
- Publicity. Registration is a modern way of making the marriage known.
Some people use an unregistered nikah to hide a second marriage or to avoid legal duties. The nikah may still be valid, but deceiving or harming a spouse is sinful. See secret nikah and court marriage. The simplest path is to register on the same day as the nikah, or soon after.
The evidence
Quran, Surah Al-Baqara 2:282
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ إِذَا تَدَايَنتُم بِدَيْنٍ إِلَىٰٓ أَجَلٍۢ مُّسَمًّۭى فَٱكْتُبُوهُ ۚ وَلْيَكْتُب بَّيْنَكُمْ كَاتِبٌۢ بِٱلْعَدْلِ ۚ وَلَا يَأْبَ كَاتِبٌ أَن يَكْتُبَ كَمَا عَلَّمَهُ ٱللَّهُ ۚ فَلْيَكْتُبْ وَلْيُمْلِلِ ٱلَّذِى عَلَيْهِ ٱلْحَقُّ وَلْيَتَّقِ ٱللَّهَ رَبَّهُۥ وَلَا يَبْخَسْ مِنْهُ شَيْـًۭٔا ۚ فَإِن كَانَ ٱلَّذِى عَلَيْهِ ٱلْحَقُّ سَفِيهًا أَوْ ضَعِيفًا أَوْ لَا يَسْتَطِيعُ أَن يُمِلَّ هُوَ فَلْيُمْلِلْ وَلِيُّهُۥ بِٱلْعَدْلِ ۚ وَٱسْتَشْهِدُوا۟ شَهِيدَيْنِ مِن رِّجَالِكُمْ ۖ فَإِن لَّمْ يَكُونَا رَجُلَيْنِ فَرَجُلٌۭ وَٱمْرَأَتَانِ مِمَّن تَرْضَوْنَ مِنَ ٱلشُّهَدَآءِ أَن تَضِلَّ إِحْدَىٰهُمَا فَتُذَكِّرَ إِحْدَىٰهُمَا ٱلْأُخْرَىٰ ۚ وَلَا يَأْبَ ٱلشُّهَدَآءُ إِذَا مَا دُعُوا۟ ۚ وَلَا تَسْـَٔمُوٓا۟ أَن تَكْتُبُوهُ صَغِيرًا أَوْ كَبِيرًا إِلَىٰٓ أَجَلِهِۦ ۚ ذَٰلِكُمْ أَقْسَطُ عِندَ ٱللَّهِ وَأَقْوَمُ لِلشَّهَٰدَةِ وَأَدْنَىٰٓ أَلَّا تَرْتَابُوٓا۟ ۖ إِلَّآ أَن تَكُونَ تِجَٰرَةً حَاضِرَةًۭ تُدِيرُونَهَا بَيْنَكُمْ فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَلَّا تَكْتُبُوهَا ۗ وَأَشْهِدُوٓا۟ إِذَا تَبَايَعْتُمْ ۚ وَلَا يُضَآرَّ كَاتِبٌۭ وَلَا شَهِيدٌۭ ۚ وَإِن تَفْعَلُوا۟ فَإِنَّهُۥ فُسُوقٌۢ بِكُمْ ۗ وَٱتَّقُوا۟ ٱللَّهَ ۖ وَيُعَلِّمُكُمُ ٱللَّهُ ۗ وَٱللَّهُ بِكُلِّ شَىْءٍ عَلِيمٌۭ ﴿٢٨٢﴾
O you who have believed, when you contract a debt for a specified term, write it down. And let a scribe write [it] between you in justice. Let no scribe refuse to write as Allah has taught him. So let him write and let the one who has the obligation dictate. And let him fear Allah, his Lord, and not leave anything out of it. But if the one who has the obligation is of limited understanding or weak or unable to dictate himself, then let his guardian dictate in justice. And bring to witness two witnesses from among your men. And if there are not two men [available], then a man and two women from those whom you accept as witnesses - so that if one of the women errs, then the other can remind her. And let not the witnesses refuse when they are called upon. And do not be [too] weary to write it, whether it is small or large, for its [specified] term. That is more just in the sight of Allah and stronger as evidence and more likely to prevent doubt between you, except when it is an immediate transaction which you conduct among yourselves. For [then] there is no blame upon you if you do not write it. And take witnesses when you conclude a contract. Let no scribe be harmed or any witness. For if you do so, indeed, it is [grave] disobedience in you. And fear Allah. And Allah teaches you. And Allah is Knowing of all things.
Writing down rights and obligations is commanded even for debts.
Quran, Surah An-Nisaa 4:59
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ أَطِيعُوا۟ ٱللَّهَ وَأَطِيعُوا۟ ٱلرَّسُولَ وَأُو۟لِى ٱلْأَمْرِ مِنكُمْ ۖ فَإِن تَنَٰزَعْتُمْ فِى شَىْءٍۢ فَرُدُّوهُ إِلَى ٱللَّهِ وَٱلرَّسُولِ إِن كُنتُمْ تُؤْمِنُونَ بِٱللَّهِ وَٱلْيَوْمِ ٱلْءَاخِرِ ۚ ذَٰلِكَ خَيْرٌۭ وَأَحْسَنُ تَأْوِيلًا ﴿٥٩﴾
O you who have believed, obey Allah and obey the Messenger and those in authority among you. And if you disagree over anything, refer it to Allah and the Messenger, if you should believe in Allah and the Last Day. That is the best [way] and best in result.
Lawful state requirements in permissible matters are to be respected.
Sunan an-Nasa'i 3369
Graded hasan... فصل ما بين الحلال والحرام الدف والصوت ...
"What separates the lawful from the unlawful is the daff and the voice."
A marriage should be public and known.
Sunan Abi Dawud 3594
Grading to be checked... المسلمون على شروطهم ...
"Muslims are bound by their conditions."
Agreements a Muslim enters, including with the state, are to be kept.
Where the ruling is recorded
- al-Hidaya, Kitab al-Nikah, opening chapter. The conditions of nikah: offer, acceptance and witnesses, with no requirement of registration.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Nikah, on the witnesses. Witnesses exist to make the marriage public and protect it from denial.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.