Does anyone know if there is a way to enter a custom field to a supplier bill like you can your sales invoices?, i could do with somewhere to enter order numbers

I know a way how you can add a custom field to input the order number on a purchase bill in QuickBooks Online (QBO), sis-autos. I'll guide you through the process below.

You can add a field on the bill page to enter the order number on which your customers are paying.  For QBO Plus and Essentials versions, you have the option to create up to three active custom fields. While for QBO Advanced, you can make up to twelve active custom fields.

To add a custom field, please follow these steps:

1. Go to the Gear ⚙ icon then select Custom fields under Lists.
2. Click on the Add custom field. If you've already created one before, you'll see the Add field instead.
3. Name your custom field. 
4. Choose the type of data that will go into your custom field: Text and number, Number only, Date, or Dropdown list. When you choose the Dropdown list, enter the items in the list.
5. Select the category the custom field belongs to Customer, Transaction, or Vendor. In your case, select Vendor since this is for your bills.
6. Make sure to put a checkmark on the Bill box. If you want to add this to other forms, put a checkmark next to the form.
7. When done, select Save.

You can check this article for more details about custom fields: Add custom fields to sales forms and purchase orders in QuickBooks Online.

Now, the additional field can be displayed on the bill.

For your future reference, visit this article for more information about personalising your sales forms: Customise invoices, estimates, and sales receipts in QuickBooks Online.

I'm still open to your replies if you need further assistance adding custom fields to your bills. We're always here to assist you all the way. Take care.