Customize invoices adding and removing fields import custom invoice templates which subscription plan of QB Online do I need to have?

I've got you covered, @blueoceanh2.

In QuickBooks Online (QBO), you can add a custom field to your invoices if you have subscribed to QBO Plus or Advanced. However, in the Plus subscription, you are limited to only 3 custom fields that apply to all sales forms.

On the other hand, with the QBO Advanced subscription, you can have up to 12 active custom fields for each type of form. Although you can't remove these fields, you can make them inactive if you don't want to use them.

Moreover, in response to your second question, please know that importing a custom template in QBO is not possible as this feature has been discontinued.

QuickBooks offers a wide range of customizable invoice templates that can be tailored to suit your business needs.

With that being said, I encourage you to create a custom template for your invoice in the Custom form styles in QuickBooks instead of importing one. This way, you can personalize it and use it as your invoice template when you create an invoice. Let me show you how:

1. Navigate to the Gear icon, then Custom form styles.
2. Click the New style dropdown, then select Invoice.
   
3. Design your template according to your preference.
4. Hit Done after.

For more details about customizing the sales forms, we can take a look at this article: Customize invoices, estimates, and sales receipts in QuickBooks Online.

I've added this article to learn how to record payments when you receive customer invoice payments: Record invoice payments in QuickBooks Online.

If you have further questions about managing invoices and subscriptions in QBO, please let me know the details below. I'll add some guides and steps to help you complete your tasks.