Essentially countries are forming a cartel to set bottom income tax. Forming cartels by private companies to „fix” prices is illegal, but countries are free to do it.
However, the actual mechanics of that tax is hard:
1. Countries can still do subsidies, but avoid touching income tax.
2. Taxing by income where revenue is generated is hard to compute. It would make sense to enforce it only on big multinationals. E.g. Big tech pay income taxes proportional to revenue from different countrues or/and where they employees are located.
3. Looking at statistics the ideal income tax floor should be around 19%.
Countries are supposed to in the end benefit people who live in those countries. There are many things that countries do that private companies can't, like jail people without their consent, for example.
On point 1., EU countries can't do state subsidies. It's illegal under Single Market rules. It was one of the arguments for Brexit that if they leave they can engage in state subsidies again.
However, the actual mechanics of that tax is hard:
1. Countries can still do subsidies, but avoid touching income tax.
2. Taxing by income where revenue is generated is hard to compute. It would make sense to enforce it only on big multinationals. E.g. Big tech pay income taxes proportional to revenue from different countrues or/and where they employees are located.
3. Looking at statistics the ideal income tax floor should be around 19%.