How do I keep track of employee payroll when several of them work at an alternate location on Wednesdays only?

Hello there, jcgrant4977.

In QuickBooks Online Payroll, taxes for employees are calculated based on their work location. Since you have employee's working in a different state, you can follow these steps to set up another work location:

1. On the left panel, click Workers.
2. From the Employees page, click the employee's name.
3. Click the Pencil icon next to Employment.
4. Click the Work Location drop-down list, and select New Work Location.
5. Enter the new address and click OK.
6. Click Done.

Please keep in mind that some states have reciprocity agreements. This means that your employee might be subject to taxes in other locations. 

You can also check this article for more information about the state agreement: About Multistate Employment Payroll Situations.

Feel free to reach out to us if you have any other questions. Thanks.