if so, if you are filing 485 for yourself only, and if you are currently working for the 140 petitioner, probably you can get away without tax return. include pay stubs, w2, and employemnt letter to reduce chances they ask for tax return.
if the derivative is filing 485 together with you, chances are good that you will need to turn in tax return, because you are going to tax return etc in lieu of I-134 to clear public charge issue.
There are other solutions but don't want to talk more since not sure if that's your case