NEC ECS: Interest charges on subcontract payments

Can a main Contractor refuse to authorize payment of interest charges which are being applied to late payments and issue a pay-less notice which excludes the value of interest charges?

The Contractor would be in breach of contract if interest that the Subcontractor was entitled to wasn’t paid. You’d then run the risk of an adjudication and possibly end up owing interest on the interest.

James, why would a Contractor not want to pay interest that was presumably due to the Subcontractor?

If the amount assessed by the Subcontractor is incorrect then assess it at the correct amount, even if that amount is zero. Whatever the amount payment the sum which is due.