Third Normal Form (1NF)
The Third Normal Form has one more additional requirement :
A. It should meet all the requirements of the second normal form.
B. It should remove columns that are not dependent upon the primary key.
In the Third Normal Form all columns depend upon the primary key. When one column depends upon the other column, table break the rule and turns into the dependency on the primary key.
Tables are not in Second Normal Form because tax depends on price, not item.
Tables are now in Third Normal Form.
Recommend the tutorial