The document discusses the employer's right of set-off under a construction contract. It defines set-off as a deduction by the employer of debt owed by the contractor. There are two pre-conditions for a set-off: 1) the contractor commits a breach of obligation and 2) fails to rectify defects as instructed. The document outlines various contract clauses where set-off can be applied if the contractor fails to meet obligations, such as failure to comply with instructions or insure works. It provides the procedures for setting off amounts, including giving notice and allowing contractor objections to be resolved by adjudication or arbitration if needed. Set-off and liquidated damages are handled separately from interim payments.