The meaning of documents under section 131 of the Income Tax Act is not defined in the act itself. But we can take guidance from decisions by various high courts. Here are excerpts of courts orders in which the Hon’ble High Court tried to explain the meaning of documents.
Meaning of documents defined by court
The phrase ‘documents‘ used in section 131 of the Income Tax Act came up before Hon’ble Bombay High Court in Avinash Bhosale vs. Union of India  322 ITR 381 (Bom.) and it explained.
Meaning: Document does not include a passport. If by an interpretative process the apex court has held that even a court cannot impound a passport, then it would be highly inappropriate to interpret the term ‘documents’ used in section 131(3) so as to enable the executive authorities to impound the passport.
Section 131 of Income Tax Act
Power regarding discovery, production of evidence, etc.
131. (1) The Assessing Officer, Deputy Commissioner (Appeals), Joint Commissioner, Commissioner (Appeals), Principal Chief Commissioner or Chief Commissioner or Principal Commissioner or Commissioner and the Dispute Resolution Panel referred to in clause (a) of sub-section (15) of section 144C shall, for the purposes of this Act, have the same powers as are vested in a court under the Code of Civil Procedure, 1908 (5 of 1908), when trying a suit in respect of the following matters, namely :—
(a) discovery and inspection;
(b) enforcing the attendance of any person, including any officer of a banking company and examining him on oath;
(c) compelling the production of books of account and other documents; and
(d) issuing commissions.
(1A) If the Principal Director General or Director General or Principal Director or Director or Joint Director or Assistant Director or Deputy Director, or the authorised officer referred to in sub-section (1) of section 132 before he takes action under clauses (i) to (v) of that sub-section, has reason to suspect that any income has been concealed, or is likely to be concealed, by any person or class of persons, within his jurisdiction,
then, for the purposes of making any enquiry or investigation relating thereto, it shall be competent for him to exercise the powers conferred under sub-section (1) on the income-tax authorities referred to in that sub-section, notwithstanding that no proceedings with respect to such person or class of persons are pending before him or any other income-tax authority.
(2) For the purpose of making an inquiry or investigation in respect of any person or class of persons in relation to an agreement referred to in section 90 or section 90A, it shall be competent for any income-tax authority not below the rank of Assistant Commissioner of Income-tax, as may be notified by the Board in this behalf,
to exercise the powers conferred under sub-section (1) on the income-tax authorities referred to in that sub-section, notwithstanding that no proceedings with respect to such person or class of persons are pending before it or any other income-tax authority.
(3) Subject to any rules made in this behalf, any authority referred to in sub-section (1) or sub-section (1A) or sub-section (2) may impound and retain in its custody for such period as it thinks fit any books of account or other documents produced before it in any proceeding under this Act :
Provided that an Assessing Officer or an Assistant Director or Deputy Director shall not—
(a) impound any books of account or other documents without recording his reasons for so doing, or
(b) retain in his custody any such books or documents for a period exceeding fifteen days (exclusive of holidays) without obtaining the approval of the Principal Chief Commissioner or Chief Commissioner or Principal Director General or Director General or Principal Commissioner or Commissioner or Principal Director or Director therefor, as the case may be.
In this article, you can get guidance from high courts on the meaning of documents under section 131 of the Income Tax Act.
Updated up to Finance Act 2021.