Courts should bear in mind the object and scheme of the entire Act, while construing its provisions. A particular provision can not be considered as interpreted in isolation so as to give room for conflict interse between the provisions of the same Act:
Assam Co. Ltd vs. state of Assam  248 ITR 567.
Life insurance comp. of India vs CIT  219 ITR 410.
Rationality: – Interpretation which does not stand the test of rationality and will lead to absurd results can not be accepted.
Oxford university press vs CIT (2001) 247ITR.658.
Absurdity: – Interpretation of a statutory provision which will result in an absurd situation should be avoided.
The duty of the court is to read the section , understand its language and give effect to the same. If the language is plain, the fact that the consequence of giving effect to it may lead to some absurd result is not a factor to be taken into account in interpreting a provision. It is for the legislature to step in and remove the absurdity
CIT vs. Vegetable Products Ltd.  88 ITR 192.
To avoid Provisions becoming ultravires courts should bear in mind that while interpreting a provision of an Act on interpretation leading to the provision becoming ultra vires should be avoided.
Assam Co. Ltd vs State of Assam  248 ITR 567.
Setting and language of entire group.
In trying to interpret a statutory provision, attention should be given to the setting in which the provision occurs and regard must be had to the language of an entire group of connected provisions which may form an integral whole.
Kerala State co-operative marketing federation Ltd vs CIT (1998) 231 ITR 814
Interpretation Clause: –
In Interpretation Clause which extends the meaning of a word does not take away its ordinary meaning. An Interpretation Clause is not meant to prevent the word receiving its ordinary, popular and natural sense when ever that would be properly applicable, but to enable the world as used in the Act. When there is nothing in the context or the subject matter to the contrary, to be applied to something to which it would not ordinary be applicable.
CGT VS Getti Chettiar  82 ITR 599.
No word to be excluded or word added: –
It is impermissible for the court to read into a taxing provision any word which are not there or exclude words which are there.The words found in the provision must be given their natural meaning: CED vs Kana kasa bai  89 ITR 251.
Each and every word to be given meaning:
Just as it is not permissible to add words or to fill in a gap or lacuna,similarly it is of universal application that effort should be made to give meaning to each and every word by the legislature: Mohammad Ali khan vs CWT (1997) 224 ITR 672.
Conflict between two independent provisions of law
If there is an apparent conflict between two independent provisions of law, the special provision must prevail.
Union of India vs India Fisheries Pvt Ltd  57 ITR 331.
Unless there is any ambiguity it would not be open to the court to depart from the normal rule of construction which is that the intention of the legislature should be primarily gathered from the words which are used.It is only when the words used are ambiguous that they should stand to be examined and construed in the light of surrounding circumstances and constitutional principal and practice: CIT vs Sodra Devi  32 ITR 615.
A casus omissus can not be applied by the court except in the case of clear necessity and when reason for it is found in the four corners of the statute itself but at the same time a casus omissus should not be readily inferred and for that purpose all the parts of a statute or section must be construed together and every clause of a section should be construed with reference to the context and other clauses thereof so that the construction should be put on a particular provision makes a consistent enactment of the whole statute. This would be more so if literal construction of a particular clause leads to manifestly absurd or anomalous results which could not have been intended by legislature:
CIT vs National Taj Traders  121 IOTR 535.
NO SCOPE FOR IMPORTING WORDS WHICH ARE NOT THERE
There is no scope for importing into the statute words which be not there. Such Importation would be not to construe but to amend the statute. Even if there be a casus omissus the defect can be remedied only by legislation and not by judicial interpretation.
TARULATA SHYAM VS CIT 108 ITR 345
Contemporaneous Exposition: –
The rule of construction by reference to contemporaneous exposition is a well established rule for interpreting a statute by reference to the exposition it has received from contemporary authority, though it must give way where the language of the statute is plain and unambiguous.
VER GHESE VS ITO  131 ITR 597
Courts in construing a statute or notification, will give must weight to the interpretation put upon it at the time of enactment or issue and since, by those who have to construe, execute and apply the said enactment.
COLLECTOR OF CENTRAL EXCISE VS PARLE EXPORTS PVT LTD  183 ITR 624.
WORDS IN A SECTION; –
Words in a section of a statute are not to be interpreted by having those words in one hand and the dictionary in the other hand. In spelling out the meaning of the words in a section , one must take into consideration the setting in which those terms are used and the purpose that they are intended to serve.
CGT vs Getti chettiar (1971) 82ITR 599