What type of tax authority provides unofficial interpretations and has limited weight in tax disputes?

The correct answer is secondary authority. Secondary authorities consist of interpretations and writings that explain, analyze, or summarize the primary tax laws and regulations but do not hold the same persuasive power as primary authority. Examples of secondary authorities include tax research services, legal commentaries, tax encyclopedias, and interpretations by practitioners that help clarify complex tax issues. While these sources are valuable for providing insights and context, they do not have the binding legal authority that primary sources, such as statutes, regulations, and court cases, possess. Therefore, in tax disputes, secondary authority may be referenced to support an argument, but it does not carry the same weight or enforceability as primary authority.