I work 4 days a week for a UK based employer, without a Dutch subsidiary. I want to be based in the Netherlands. As far as the actual work is concerned, I can do this, as all is online. Presumably I need to pay tax in both places as a basic rule of thumb. Presumably there is a double taxation treaty UK-Netherlands which might help. BUT regardless of that, regardless of affordability, is it LEGAL? If I am to apply for residency, as a self supporting individual, does the Dutch tax system demand that the UK employer pay social security contributions and other at source taxation, or can one pay this voluntarily into the Dutch system? Presumably the Dutch system understands this near full time work not as freelance work and therefore won't allow you to pay contributions voluntarily...I know my UK employer will not pay into the the Dutch system directly.