What document details taxes and allocations in an annual financial statement?

The Union Budget is the correct answer because it encompasses the government's taxation policies, allocations for various sectors, and the fiscal stance for that financial year. It serves as a comprehensive financial plan that outlines expected revenue from taxes and government spending. This document is crucial as it informs stakeholders, including businesses and the public, about how the government plans to collect and allocate financial resources.

In contrast, the other options do not serve the same purpose. A Cabinet Memorandum is typically a document used to communicate decisions and policies within the cabinet, lacking the extensive financial details found in the Union Budget. A Fiscal Report, while related to financial matters, generally summarizes the government's budgetary performance rather than detailing tax policies and allocations. A Financial Statement is a broader term that can refer to various financial documents prepared by an entity, including income statements and balance sheets, but it does not specifically denote the government’s taxation and allocation strategies for a financial year like the Union Budget does.