Several states, including Sweden, are considering introducing rules on the duty of disclosure for tax advisors, and in some states such rules have already been introduced. Rules on the duty of disclosure for tax advisors mean that under certain conditions a legal advisor must provide information directly to the tax authority, i.e. in addition to the information provided by the taxpayer in his or her tax return. For the tax authorities, this can constitute a new source of information that can enable more cost-effective taxation than traditional review of tax returns and investigation in connection with so-called tax audits. However, it is considered a fundamental right in a state governed by the rule of law to be able to seek legal advice without having to worry about the legal advisor passing on information about what has been said to someone else. Rules on the duty of information for tax advisors risk being in conflict with this right. This study aims, among other things, to investigate the possibilities of designing such rules so that they do not infringe on fundamental rights.