Mika is an employee of Nokian Renkaat Oyj, a Finnish company engaged in manufacturing tyres. He is an engineer, working on tyre compounds. He lives (or rather used to live) in Nokia, Finland, and has been working at the headquarters of the company (also in Nokia, Finland) since he joined the company (in 2010). In January 2015 the company opened a new tyre-testing facility in the south of Spain. The facility was intended to be used (and indeed was used) to test how tyres cope in extreme heat. In late 2017 Mika was offered an opportunity to spend some time working at the new facility (as an input of a tyre-compound engineer was unexpectedly required in view of unexpectedly high number of failures of new tyres tested there), and he accepted, moving to Spain in January 2018. Mika ended up living in Spain until the end of 2020, returning permanently to Finland in January 2021.

3.1. Which country would get Mikas payroll taxes for 2018 and 2019? Does it depend on the type of tax, or an any formalities being complied with? If yes, then how?

3.2. If instead of returning to Finland in January 2021 Mika decided to stay permanently in Spain, which country would get Mikas payroll taxes from January 2021 onwards? Does it depend on the type of tax, or an any formalities being complied with? If yes, how?