Hi MartinSykes,
Thank you for answering the questions of my colleagues.
The answer to your question above is Yes. QuickBooks needs to know the tax code to calculate the employee's tax, particularly the PAYE tax.
For additional reference, you can check the GOV.UK website and click on PAYE tax calculator. You'll see that the employee tax code is one of the needed factors in calculating the PAYE tax.
Feel free to visit us back here if you need anything else.
