GBA means municipal basic administration of personal data
The GBA has personal data from anyone who is resident in the Netherlands (or has lived). This information is used by the Government to make your passport and driver's license, but also to check who can vote. The information is, as the abbreviation already has, basic information (name, address, date and place of birth, civil service, nationality, parents, children, electoral rights, etc. If you are going to move or get a child, you have to pass this on to the GBA, but if you marry (in the Netherlands) you do not have to, then the civil servant will arrange for this. The Tax Office and the Social Insurance bank use the data in the GBA to keep the information up to and relevant.