Payroll and STP

Allow me to illustrate a workaround so you can save an employee's legal name (first name) without a surname in QuickBooks, Sharon.

Since QuickBooks requires you to enter a Surname in the employee's profile, the best option is to enter a special character in this field. For this, you can enter a period " . " as the employee's Surname to bypass the error you've encountered. See the sample snapshots below.

Entering period " . " in the Surname section when editing the employee's information:

After saving the modification you've input, the Employee name will shown in this sequence: First Name followed by the period as the Surname:
 

Still, it's best that you contact your client's bank again to verify if they'll accept this method as a workaround. By doing so, you can notify them that QuickBooks requires you to enter a Surname to save your employee's profile. This way, they'll be fully aware of the situation and can advise you with more suitable alternatives that align with their policy.

I've also added this article that might be handy for you: Reimburse an employee in QuickBooks Online. You can utilize it if you need to compensate employees for business-related expenses using their personal funds.

Confirming this process with your client's banking institution ensures you can set your employee's details accordingly in QuickBooks. If you have more questions about managing an employee's profile, revisit this thread so we can guide you thoroughly.