One suggestion: could you separate the code and tax slab configuration, different files.
Actually, separating out the things should be modified from things that shouldn't would be a significant improvement. Like:
# Section 1: Configuration: Change this as appropriate:
FOO =
BAR =
# Section 2: Logic: Don't change this:
...
Actually, separating out the things should be modified from things that shouldn't would be a significant improvement. Like:
# Section 1: Configuration: Change this as appropriate:
FOO =
BAR =
# Section 2: Logic: Don't change this:
...