After Mexico's independence from Spain in 1821, the Philippines which had previously been administered as part of the Viceroyalty of Mexico came under direct administration by Spain. By the 1840s it became clear that the islands' surnaming practices were causing difficulties in administration and the collection of taxes: siblings would often take different surnames, many repeat names derived from Catholicism were extant, such as de la Cruz or delos Santos, causing confusion in bureacratic documents.

The governor General in 1849 issued what became known as the Claveria decree, specifically citing the above as a need for issuing new surnames. Along with the decree a book was issued to provincial leaders: Catálogo alfabético de apellidos. The decree cited the precedures, exemptions, and processes by which every Filipino household head would select a new single surname for their entire family and the new surnames be recorded. Certain exemptions were issued for:

1. Families with existing surnames that were not considered too common already

2. Families named after saints (as long as it was not far too common such as de la Cruz or delos Santos) provided they could prove they'd been using it for four generations already.

The entire Claveria decree can be read in English translation in full [here](After Mexico's independence from Spain in 1821, the Philippines which had previously been administered as part of the Viceroyalty of Mexico came under direct administration by Spain. By the 1840s it became clear that the islands' surnaming practices were causing difficulties in administration and the collection of taxes: siblings would often take different surnames, many repeat names derived from Catholicism were extant, such as de la Cruz or delos Santos, causing confusion in bureacratic documents and especially the cedula or community tax. (as an interesting aside we still have a small token tax here called the cedula that can be used to register and verify your place of residence and as a partial form of identification)

The Catálogo included both Spanish and indigenous derived names and the heads of households were allowed to choose their names, though sometimes with some constraints imposed by provincial heads such as requiring a single town to choose names only starting with a single letter.

Sources: The entire Claveria decree can be read in English translation in full here .

The Catálogo alfabético de apellidos is in the national archives in Manila, but unfortunately I can't find a full upload of it online.