The amount of a lien claimed by a subcontractor may not exceed:
(1) an amount equal to the proportion of the total subcontract price that the sum of the labor performed, materials furnished, materials specially fabricated, reasonable overhead costs incurred, and proportionate profit margin bears to the total subcontract price; minus
(2) the sum of previous payments received by the claimant on the subcontract.
Official text of the Texas Property Code as published by the Texas Legislative Council.