Data of 1.2 million individuals and 200,000 companies were stolen in a large-scale cyberattack, DPA reported, citing a statement from Latvia's Road Traffic Safety Directorate (CSDD).
Names, payment details, vehicle registration numbers and an address registered on the day of the service were reportedly stolen.
Latvia has a population of around 1.9 million.
It is unclear who is behind the incident.
Prime Minister Andris Kullbergs said that the involvement of another country could not be ruled out, according to the news agency Leta.
Kulbergs criticized the CSDD leadership for informing him about the data theft too late.
He mentioned a previous hacker attack on the state forestry administration in June.
Two "serious cyber incidents" that occurred within a short period were a clear signal that additional security measures were needed, he said. "This is now literally a matter of national security," Kulbergs said.