Let me chime in and share some insights with you.

You'll want to check the account of your sister company they've already set up or connected to QuickBooks Payments account. If not, don't worry, I'll show you how.

First, refund any outstanding transactions before connecting our accounts, as you will not be able to refund transactions created prior to the date you connect your payments account. You should also delete any recurring payments in Merchant Services. Before you begin, Sign in to Merchant Services and disable recurring payments.

Next, you can follow these steps to connect your payments account to QuickBooks Online:

1. Sign in to QuickBooks Online as an admin.
2. Go to Settings ⚙, then select Account and settings.
3. Choose Payments.
4. In the Existing account section, click Connect or Link Merchant Service.
5. Choose the QuickBooks Payment account you want to connect to. Then click Connect.
6. Review the account info and make sure it's accurate. If everything looks good, tick Connect.
7. When the connection is finished, sign out and sign back into QuickBooks Online.

For detailed information and steps, refer to this article: Connect your QuickBooks Payments account to QuickBooks Online.

I'll be adding this article so you can read and learn how to personalize and add specific info to your sales forms in QBO: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Feel free to reach us again for further concerns. Stay safe!