Personal Income provides statistics on the population's incomes and tax payments as well as the distribution of incomes. It contains information on incomes at both the personal and family level as well as data on the distribution of income. The Income is available both pre- and post-taxes and can be split into sub-categories such as primary incomes, transfers, property income and taxes etc.
The population is divided into groups by age, Socio economic status, gender, municipalities (NUTS 3), and type of family and into income intervals. Data is collected and published yearly.
The primary source is administrative data from the Danish tax authorities. Using secondary sources from the municipalities and unemployment funds the incomes are subdivided into more detailed types of income. Finally other registers in Statistics Denmark, such as the population register, provides background information.
Data related to income is collected monthly or annually from the Tax Authorities or Udbetaling Danmark, which pay out transfers in Denmark.
You can expect revision with each historical update.
More information can be found at: http://www.dst.dk/en/Statistik/dokumentation/declarations/income-statistics.aspx