I agree double negatives are always hard to get your mind around and aren't in the 'plain English' style which NEC aspires to be in.
The reason for it, though, is to avoid double deductions. E.g. the Contractor deducts retention from a Subcontractor and then has a further deduction on top from the Employer (NEC3) or Client (NEC4)
The reason for it, though, is to avoid double deductions. E.g. the Contractor deducts retention from a Subcontractor and then has a further deduction on top from the Employer (NEC3) or Client (NEC4)