In accordance with Section 14, 3. part of Register of Natural Persons Law a citizen of Latvia, a non-citizen of Latvia, a foreigner who has received a residence permit, registration certificate or permanent residence card in Latvia, shall have a duty to provide the information to the Office of Citizenship and Migration Affairs regarding changes in the information included in the Register of Natural Persons about him/her, his/her minor children and persons, being under his/her custody or guardianship, which were made by foreign authorities (for example, entering into marriage, dissolution of marriage, change of the surname etc.).
The documents should be sent directly by post or by e-mail signed with an electronic identification to the Office of Citizenship and Migration Affairs of the Republic of Latvia. More detailed information can be found here