A lien waiver is a written, signed document in which a contractor, subcontractor, or supplier waives their right to file a mechanic's lien against the project property in exchange for payment received or about to be received. Lien waivers come in four standard forms: conditional partial, unconditional partial, conditional final, and unconditional final.
Conditional waivers take effect only when the payment they reference actually clears. Unconditional waivers waive lien rights immediately upon signing. Partial waivers cover progress payments to date; final waivers cover the entire project balance. Best practice for owners and GCs is to require conditional waivers with each progress payment and unconditional final waivers at project completion. Best practice for subs is to never sign an unconditional waiver before the underlying payment has actually cleared the bank.