Entering a tax code in item 00001 is the official act of filing and documenting a unique form of identifying information required by the government for tax purposes. This data may include taxes that are due from an individual or business, as well as any applicable exemptions or deductions. When filling out forms for tax purposes, it is important to ensure accuracy and completeness of all applicable codes. By entering these codes in item 00001, it ensures that the tax amount due is accurately accounted for and filed properly.