Hi Chelsie,
IncomeTax is calculated and charged when the Income is paid.
The Personal Allowance is used on a weekly or monthly basis depending on how often you are paid.
If you are earning more with the placement, you should have the allowance allocated against this.
We always review the position after the tax year has ended and if you pay too much tax you will receive a P800 calculation once we have reviewed it.
Please see this guidance here:
Tax codes
Thank you.