Section 50, The Public Procurement Act, 2016

(1) Subject to subsection (2) of section 28, a bid shall notbe accepted unless submitted in writing, duly signed, in a sealed envelope within the deadline for submission of bids and any bid received after the deadline for submission of bids shall be returned unopened. (2) Invitation for bidding and prequalification documents shall permit submission of applications to bid or prequalify by hand or mail or by courier at the option of the bidder. (3) The Authority may by statutory instrument prescribe– (a) other methods of submission of bids, such as by electronic mail; (b) rules for the protection of the confidentiality and security of bids, including the prevention of the opening and reading of bids by anyone until the time set in accordance with paragraph (d) of subsection (3) of section 49. (4) Bids shall remain valid for the period of time indicated in the bidding documents, but modification or withdrawal of a bid during the bid validity period is subject to forfeiture of the bid security. (5) The validity period of a bid may be deemed extended only on the basis of the agreement of the bidder concerned and bidder that agrees to an extension of the validity period of its bid shall also obtain a corresponding extension of the bid security, if such a security was required.