The consequences can be particularly severe. In the case discussed (TF 9C_39/2023), the taxpayer believed he was limiting his voluntary disclosure to wealth tax. However, since he was unable to prove that the funds were from a non-taxable source (inheritance, gift, or statute of limitations on income tax having expired), the tax authority also assessed additional income tax. This resulted in a significant financial burden, including back taxes, a fine, and interest on arrears accumulated over several years. The total amount exceeded the value of the undeclared assets.