Does it mean I can contact the support team on Monday only?

Hello there. I'll help you get routed to the appropriate support to ensure your queries are answered.

Our online support experts are available 24 hours a day, Monday through Friday, GMT. To contact support, you can follow these steps:

1. Open your QBO account.
2. Select Help (?).
3. Click Contact Us and choose a way to connect with us:
    

• Start a chat with a support expert.
• Get a callback from the next available expert.

Do you have any specific concerns regarding the custom form styles for tax invoices? If so, you can also add them in your reply so we can provide an accurate answer. 

Once everything's fine, you might want to check this article and learn how to add custom fields to your sales forms and purchase orders: Add custom fields to sales forms and purchase orders in QuickBooks Online.

 Feel free to comment if you require additional assistance with our support team, tax invoices, or any QuickBooks-related queries. I'll handle them for you. Have a great day ahead.