You are required for marriage registration in most of countries because they are signatories to the UN convention on registration of marriages. The UN General assembly adopted the first convention in 1964. It was again made compulsory in 1979 when the Convention on the Elimination of All Forms of Discrimination against Women (CEDAW) was adopted. The registration was important. It has become essential when usage of internet dating sites is increasing. Geographical, racial and language differences are no more restricting the people from choosing their desired spouses all over the world.
Muslim marriages are not an exception!
Islamic marriages are valid even when unwritten. An offer and acceptance is required in one meeting where at least two witnesses are available. But due to importance of registration of marriage, many countries have coded laws to make non-registration of marriage a criminal offense punishable with imprisonment or fine or with both.

Registration of Marriages in Pakistan
Section 5 of the “Muslim Family Laws Ordinance 1961” provides that every marriage solemnized under Muslim marriage law must be registered. The local union council is empowered to appoint marriage registrars in every ward of the council.
Registration of Marriages in India
Section 15 of Indian Special Marriage Act 1954, provides that any marriage celebrated may be registered by a Marriage Officer in the territories to which this Act extends. The sub-sections give details of necessities and prohibitions for marriage registration. The conditions involve number of spouses, mental state and age of the contracting parties. The law also provides that no marriage can be registered if the parties are within the degrees of prohibited relationship.
The National Commission for Women proposed compulsory registration of all marriages in 1992. A year later, while ratifying ‘Convention of Elimination of all forms of Discrimination Against Women, the Indian government has inserted a reservation regarding the minimum marriage age and compulsory registration of marriage stating that “it is not practical in a vast country like India with its variety of customs, religions and level of literacy.”
In Other Countries
Most of the countries require that a Muslim marriage must be registered. Indonesia’s National Marriage Act has made marriage registration compulsory in parts of the country dependent on evidence that the marriage is neither forced nor polygamous. Kuwait qualifies the parties at the age of puberty and of sound mind to enter a Muslim marriage contract. It makes marriage registration compulsory where the female has reached to the age of 15 years and male of 17 years.
Being signatories of the UN conventions, the governments recognize marriage registered in any country as registered within its boundaries. Suppose you register your marriage in Pakistan and go to U.K, you need not to register your marriage again. However, you may be required to show your registered marriage certificate.