You can efficiently manage both your company's payroll data using your subscription, @ELM. Let me share some valuable information about this.

QuickBooks Desktop Enhanced Payroll allows you to manage up to 50 Employer Identification Numbers (EINs). You can also add another company file to your subscription if it hasn't used QBDT Payroll before. If it has, please contact our customer care team for a service key. 

To add your company file, here's how:
 

1. Go to Employees menu, then Payroll.
2. Select Use My Existing Payroll Services.
3. Select Add File from the Account Maintenance window.
4. After that, navigate to the Add to Subscription Number radio button. Please note that if this option isn't available a payroll service has already been validated in the company file.
5. You can choose the Other: I have an existing subscription, if your subscription isn't listed.
6. Once done, input your subscription number and Zip Code.
7. Select Next twice, then Print or Return to QuickBooks.
    

For more information, you can read this article: Add a new company to your payroll subscription.

I'll also include these articles you can read if you need guidance in managing your payroll e-filing in QuickBooks: 

• E-file payroll tax forms for your clients
• Handle payroll e-file and e-pay rejections

If you have other questions or need further assistance in handling your payroll and employees, please don't hesitate to reach out to this forum, @ELM. We're always around to help.