I was able to add a custom field in purchase order but unable to copy that custom field during billing. Is there a way that it will also show in the billing from PO?

Good to see you here in the Community forum, @Fadi-luztan. I'll be glad to share information about the custom field in your purchase order that doesn't show when creating bills.

The option to show a custom field in a Purchase Order and have it automatically transfer to a Bill in QuickBooks Online is not available. Custom fields created in the Purchase Order form do not currently carry over to the Bill form when linking the two transactions.

I know this functionality would be beneficial to your business. I'd recommend sending a feature request directly to our Product Development team. Doing so helps us improve your experience and the features of the program. 

Here's how:

1. Select the Gear icon at the top, then Feedback.
2. Enter your comments or product suggestions.
3. Then select Next to submit feedback.
   

I'm adding this article for you to keep track of the feedback request you've sent: Customer Feedback for QuickBooks Online.

If you need to customize your sales forms and add custom fields, you can refer to these articles for detailed instructions:

• Customise invoices, estimates, and sales receipts in QuickBooks Online.
• Add custom fields to sales forms and purchase orders in QuickBooks Online

If you have any suggestions or concerns regarding QuickBooks, please feel free to let me know in the comments below. I'm here to answer all of your questions and provide assistance. Take care and stay safe.