Section 30(2)(ii) in The Central Government Account (Receipts and Payments) Rules, 1983
(ii)the contractor's own acceptance of the correctness of the amount made out as being due to him by the Government; or his signature on the bill or other claim preferred against the Government before settlement of the account or claim by payment to the said bank. While the acknowledgement by a bank of cheque or draft received towards payment shall constitute a full and sufficient discharge, for the payment, contractors should, wherever possible, be induced to present their bills duly receipted and discharged through their bankers. Nothing herein contained should operate to create in favour of the bank any right or equity vis-a-vis the Government.