def update_kvk(kvk):
    """
    Function to update outdated KvK-numbers
    :param kvk: the orginal KvK-number
    :return: the updated KvK-number, if it was updated
    """

    # Make sure KvK-number is a string
    kvk = str(kvk)

    # Add zero to beginning of outdated KvK-number and return it
    if len(kvk) == 7:
        new_kvk = '0'+kvk
        return new_kvk

    # If KvK-number is up to date, just return it
    else:
        return kvk