How do I change an employee from casual to full time, with increased pay rate, mid pay period?

Hi HECLisa, 

Thank you for reaching out on this. 

You might like to consider creating a new pay rate for this employee so in the pay run which the change take place, you can seperate the number of days/hours were paid with the former pay rate and the days/hours were paid with the new pay rate as 2 seperate earning lines. 

I found these 2 articles from our Payroll support for your reference:

Updating Employee Pay Rates
- https://support.yourpayroll.com.au/hc/en-au/articles/200265374-Updating-Employee-Pay-Rates

Adding Earnings Lines To A Pay Run
- https://support.yourpayroll.com.au/hc/en-au/articles/200030979-Adding-Earnings-Lines-To-A-Pay-Run

Hope these help and please let us know if you have any follow up questions.