; (ii) all sales before a specific date; or (iii) all sales until the dealer or cash seller terminates the agreement in writing. (C) Effect on payment terms A waiver under subparagraph (A) shall not affect the payment terms of the sale. (4) Effect of dishonored instruments For purposes of determining full payment under paragraph (1), a payment to an unpaid cash seller shall not be considered to have been made if the unpaid cash seller receives a payment instrument that is dishonored. (c) Enforcement If a dealer fails to perform the duties required by subsection (b), the Secretary shall take such action as is necessary— (1) to enforce the trust, including by appointing an independent trustee; and (2) to preserve the assets of the trust. (d) Preservation of trust An unpaid cash seller shall lose the benefit of a trust under subsection (b) if the unpaid cash seller has not preserved the trust by— (1) providing a written notice to the applicable dealer of the intent of the unpaid cash seller to preserve the benefits of the trust; and (2) filing that notice with the Secretary— (A) not later than 30 days after the final date for making a payment under section 409 in the event that a payment instrument has not been received