Pricing/Resolver/TaxResolver.php
protected function resolveCustomerTargetCountry(CustomerInterface $customer): ?CountryInterface
    {
        if (null !== $address = $customer->getDefaultDeliveryAddress()) {
            return $address->getCountry();
        }

        return null;
    }
protected function resolveCustomerTargetCountry(CustomerInterface $customer): ?CountryInterface
    {
        if (null !== $address = $customer->getDefaultDeliveryAddress()) {
            return $address->getCountry();
        }

        return null;
    }
Resolves the customer's taxation target country.

@param CustomerInterface $customer

@return CountryInterface|null