If information disclosed in accordance with this chapter is subsequently rendered inaccurate as a result of any act, passage of time, occurrence, or agreement subsequent to the delivery of the required disclosures, the resulting inaccuracy does not constitute a violation of this chapter. If at the time the disclosures are required to be made, an item of information required to be disclosed is unknown or not available to the seller, the seller shall so state and may use an approximation in responding.