If you mean transfer as regards banking, the whole EU (plus EFTA and the UK) are covered by the Single Euro Payments Area, within which all bank transfers must

If you mean transfer as regards banking, the whole EU (plus EFTA and the UK) are covered by the Single Euro Payments Area, within which all bank transfers must be subject to the same rules and fees as national ones (notwithstanding currency exchange fees if applicable). If you mean transfer in a more abstract fiscal sense, not even individual EU states themselves are homogeneous regarding their internal fiscal policies. Some are federal, such as Germany, and some are highly centralised, such as France. Then you have the case of Spain where all 17 autonomous communities (≈pseudofederal states) have a small leeway regarding income tax and must follow the baseline central policy, but two regions in particular—the Basque Country and Navarre—have fully devolved powers regarding taxation due to "fueros", i.e. historical rights.