A WHMCS hook to copy Company Name and Address from Clients to Contacts (sub-accounts) upon creation of a new Contact. This ensures that invoices always show the correct Company Name and Address.

set_sub_account_info.php

<?php
if (!defined("WHMCS"))
    die("This file cannot be accessed directly");

use WHMCS\Database\Capsule;

/*
 * Copies account details from parent accounts to sub-accounts
 */
add_hook('ContactAdd', 1, "wb_setup_sub_accounts");
add_hook('ContactEdit', 1, "wb_setup_sub_accounts");
add_hook('PreCronJob', 1, "wb_setup_sub_accounts");
//add_hook('AdminAreaFooterOutput', 1, "wb_setup_sub_accounts"); //this for testing only
function wb_setup_sub_accounts(){
    //get all contacts with no company name set
    $to_setup_contacts = Capsule::table('tblcontacts')->where('companyname', '')->get();
    foreach( $to_setup_contacts as $contact ){
        $client = Capsule::table('tblclients')->where('id', $contact->userid)->get();
        if( is_array($client) && !empty($client) ){
            $client = $client[0];
        }
        
        if( null == $client || '' == $client || empty($client) ){
            continue;
        }
        
        //update contact info to match client
        $update = array(
            'companyname' => $client->companyname,
            'updated_at' => date('Y-m-d H:i:s')
        );
        if( '' != $client->phonenumber && '' == $contact->phonenumber ){
            $update['phonenumber'] = $client->phonenumber;
        }
        if( '' != $client->country && '' == $contact->country ){
            $update['country'] = $client->country;
        }
        if( '' != $client->postcode && '' == $contact->postcode ){
            $update['postcode'] = $client->postcode;
        }
        if( '' != $client->state && '' == $contact->state ){
            $update['state'] = $client->state;
        }
        if( '' != $client->city && '' == $contact->city ){
            $update['city'] = $client->city;
        }
        if( '' != $client->address2 && '' == $contact->address2 ){
            $update['address2'] = $client->address2;
        }
        if( '' != $client->address1 && '' == $contact->address1 ){
            $update['address1'] = $client->address1;
        }
        
        if( Capsule::table('tblcontacts')->where('id', $contact->id)->update( $update ) ){
            logActivity('Contact setup: Updated contact '.$contact->id.' with info from parent account. '.print_r($update,true), 0);
        }
    }
}