Custom Fields and reports

This might be a silly question and I know this is not a coding site but where do I find the number for a custom field. I have gone into the PAYG payment summary – individual non-business in settings and have added another label called Tax Type and it shows on the report.
So far so good but I want to get my employee custom field in as the answer sooo I figured I would just copy the code line above it which is
{% assign employeeTFN = report.employee.customFields[“8067ce2d-6a48-45f1-a5a9-5e2d923e9cc7”] %}
so far it looks like this
{% assign Tax type4 = report.employee.customFields[“xxxxxxxxxxxxx”] %}
but I dont know the number to put in there so how do I find out the number

You will need to complete a manual entry, then use Batch Update to see the result and get the GUID (the hexadecimal string) from that.

Thanks @Tut I tried that but it just gave me the letter that was in there oh wait I pasted as a paste special and it gave me this number 9f5abab92d544769b50c9076cc8e8e5f normally it has - inbetween the numbers/letters so I counted the Numbers/letters in one that was already in there and did the same so it now looks like 9f5abab9-2d54-4769-b50c-9076cc8e8e5f and it worked(just incase anybody else is looking for the same answer)