Doest anyone know how casual worker has to be registered in the bookkeeping?I mean those workers which only come for 1/2 days (eg. for a paid trial)?

Hello there, @info657.

You can register the casual workers as regular employees to pay them, track their paycheques, and taxes per paycheques issued. Let me show you how:

1. On the left pane, click the Employees menu.
2. Go to Employees at the top of the screen and select Add an employee. 
3. Fill in the employee's gender, date of birth, email address, and address, then click Save and next.
4. Enter the employee's start date, their pay type, and how much you pay them.
5. Select whether the employee has been paid since 6 April. Depending on your answer, you will be required to fill in different fields: Yes, by another business or Yes, by my business.
6. Click Save and next.
7. Fill in the employee's tax information, then press Save and next.
8. Review the information on the last page and press Done if you are happy with this.

If you're using PaySuite, you can refer to this article to enter your employee information: Add or update an employee record.

You can include casual employees in your regular pay schedule or set a specific schedule for them . If you're not going to pay them, you can remove the employee from this payroll by selecting the slider next to their name. 

I've included some articles below for running payroll based on the payroll version you're using:

• Pay your employees in QuickBooks Online Standard Payroll

• Creating Payroll in PaySuite

Drop me a comment below if you have any other questions. I'll be happy to help you some more.