Even if governments were perfect at ID verification it wouldn't change the argument above, right? Being perfect at verifying UBI eligibility would require a large government infrastructure, just like today, so you can't claim that the U part makes it super cheap to administer.

But no government is close to perfect. Here are some examples for your edification.

The UK doesn't even know how many people are living there, and it's an island. There's no centralized identity scheme and during COVID more people came forward for vaccination in some age bands than theoretically existed at all.

Germany fails at reliably verifying that people who turn up for a language test as part of naturalization are the same people being given citizenship: https://www.infomigrants.net/en/post/69787/germany-police-ar...

All countries struggle with basics like "is the recipient of the welfare dead". Here's a specific case where Italy didn't notice it should stop paying out a state pension (a form of UBI) for years after death, with the fraudster only getting busted when he tried to dress up as his own mother: https://www.theguardian.com/world/2025/nov/25/italian-man-dr...

Paying out money to dead people is a very common problem. Here's an EU report on all the basic ways countries get defrauded by failing to track basic facts about identities:

https://www.ela.europa.eu/sites/default/files/2025-03/SSC_fi...

"Common fraud and error cases include falsified documents (birth, marriage and death certificates), identity fraud and falsified non-payment certificates"

Even in UBI, there would be a strong expectation that each person only receives it once. But checking stuff like that requires a huge bureaucracy.