TAXes-as an ABAPer

Hi Folks,

In the coming days I will be working on Taxes in SD,MM and FI.I just want to know

1.what are the areas that as an ABAPer I need to know.?

2.What are the common problems that a technical consultant will face.

3.What are the T-codes that we come across.

4.Any tips which can be handy.

K.Kiran.