Answer:
I am assuming you are providing a final TIL. The final TIL should reflect the index value and discount/premium you used at closing. The index value could be the then current value (which is the one I suggest you use) or it can be a value within your stated look-back period.
Can you cite the Reg that supports this.
Answer: Regulation Z - 1026.18(s)(2) and its Commentary.