Even a blank cheque leaf, voluntarily signed and handed over by the accused,

"Even a blank cheque leaf, voluntarily signed and handed over by the accused, which is towards some payment, would attract presumption under Section 139 of the Negotiable Instruments Act, in the absence of any cogent evidence to show that the cheque was not issued in discharge of a debt."

https://www.livelaw.in/top-stories/subsequent-filling-of-unfilled-signed-cheque-not-alteration-142718