private function validateBusiness(string $vatNumber): bool
    {
        $weights = [1, 2, 3, 4, 5, 6, 7, 8];
        $checkval = $this->sumWeights($weights, $vatNumber);

        if ($checkval % 11 == 10) {
            $weights = [3, 4, 5, 6, 7, 8, 9, 10];
            $checkval = $this->sumWeights($weights, $vatNumber);

            $checkval = ($checkval % 11) == 10 ? 0 : ($checkval % 11);
        } else {
            $checkval = $checkval % 11;
        }

        return $checkval == (int) $vatNumber[8];
    }