This article explains the steps you can follow to find the particular Box value in Tax reporter
Lets take an example say you have run the W2 you like to know from where Box 2 values is coming, for this we need to find what is the field mapped to Box 2
1) Go to transaction SFP and Give the Form name, for W2 it is HR_F_W2_Mult_07, by looking at Object Binding for the Box 2, you will find the field name
2) Go to log manager and note down the Form number and Control Number.
3) Go to PU19 ==> Menu Utilities ==> Display Form Fields ==> you can check the field value by providing the form number
4) Open the Tax form Field Definition from the following IMG path
5) Note down the Tax form Group which is mapped to Tax form Field
6) Check whether other field also cumulate the value into this field by checking the table T5UT3 for the Tax form and Sum in field combination
7) Note down the other field name and Value which cumulating into this field
8) Open the Tax form Group from the IMG and look which Wage Types are mapped to the tax form group
9) Go to PC_Payresult and check the value’s of the Wage types
Note : It takes the value from RT not from CRT or TCRT
By following the above steps you can identify from where the values are populated into Boxes.