MPs must agree a money resolution if a bill proposes spending public money on something that hasn't already been authorised by Parliament. Before it’s agreed, a money resolution is called a money motion.
Money motions are normally put to the House for agreement immediately after second reading, in which case there’s no debate (because there’s already been a chance to talk about the money resolution in the second reading debate). If a money motion is introduced at another point during the bill’s progress, it can usually be debated for up to 45 minutes.