Citation-locked late-claim interest demand letter — the deterministic check plus a demand built on the lane's own day-count math table (TX 18%/prime+5, FL CFO quarterly factors from the notice date, NY no-fault 2%/month, AZ 10%, GA 12%, CA 15% + auto-include penalty). TX weather letters satisfy the §542A.003 pre-suit notice, element by element. Verbatim statutory quotes; the escalation is a free DOI complaint. Honest-no on unsupportable facts.