Welcome to the Community. Being able to record the prior payroll information is essential to ensure that the employee profile is up to date. QuickBooks Online offers a payroll feature with the ability to pay your employees and track your remittances. I'd be glad to point in the right direction on how to enter your employee's prior source deductions.
If you haven't run payroll in your QuickBooks account, you can click on Payroll on the left navigation menu > select Employees > choose Add an employee > follow the prompts and the last section when entering employee information will be Enter prior pay details. You'll be able to enter the prior payroll information for the employees.
If you have run any payrolls on your account, I encourage you to contact our customer service team as they can verify your account in order to enter your employee's prior source deductions in the back end. Here are the options available to reach out to our customer support team.
Schedule a Callback or start a Chat: click (?)Help in the upper right in QuickBooks Online > type and enter "Contact support" into the QB Assistant > click Contact Us > explain your situation > click Let's Talk > choose Get a callback or Start a Chat.