Unconditional Progress Release

It means discharged or allowed to leave under the circumstances on a specific date without any stipulations where no restrictions can be placed. It can be used in circumstances when the claimant has received the progress payment from the other party. 

Such documents serve as the legal agreement where it indicates the other party has already made suitable arrangement to clear the market value of the debt and the holder of the debt no more need to take further steps or fill documents to clear the lien.  

Such waivers are used when the payment has been exchanged by paying by bank transfer protection, while, it is at your disposal (like paying by bitcoin alternative currency).