First See the information sought comes under any of the following exception:-
8. Exemption from disclosure of information. —
(1) Notwithstanding anything contained in this Act, there shall
be no obligation to give any citizen,—
(a) information, disclosure of which would prejudicially affect the sovereignty and integrity of India, the
security, strategic, scientific or economic interests of the State, relation with foreign State or lead to incitement of
an offence;
(b) information which has been expressly forbidden to be published by any court of law or tribunal or the
disclosure of which may constitute contempt of court;
(c) information, the disclosure of which would cause a breach of privilege of Parliament or the State
Legislature;
(d) information including commercial confidence, trade secrets or intellectual property, the disclosure of
which would harm the competitive position of a third party, unless the competent authority is satisfied that larger
public interest warrants the disclosure of such information;
(e) information available to a person in his fiduciary relationship, unless the competent authority is satisfied
that the larger public interest warrants the disclosure of such information;
(f) information received in confidence from foreign Government;
(g) information, the disclosure of which would endanger the life or physical safety of any person or identify
the source of information or assistance given in confidence for law enforcement or security purposes;
(h) information which would impede the process of investigation or apprehension or prosecution of offenders;
(i) cabinet papers including records of deliberations of the Council of Ministers, Secretaries and other officers:
Provided that the decisions of Council of Ministers, the reasons thereof, and the material on the basis of which
the decisions were taken shall be made public after the decision has been taken, and the matter is complete, or
over:
Provided figther that those matters which come under the exemptions specified in this section shall not be
disclosed;
(j) information which relates to personal information the disclosure of which has no relationship to any public
activity or interest, or which would cause unwarranted invasion of the privacy of the individual unless the Central
Public Information Officer or the State Public Information Officer or the appellate authority, as the case may be,
is satisfied that the larger public interest justifies the disclosure of such information:
Provided that the information which cannot be denied to the Parliament or a State Legislature shall not be denied
to any person.
(2) Notwithstanding anything in the Official Secrets Act, 1923 (19 of 1923) nor any of the exemptions permissible
in accordance with sub-section (/), a public authority may allow access to information, if public interest in disclosure
outweighs the harm to the protected interests.
(3) Subject to the provisions of clauses (a), (c) and (i) of sub-section (/), any information relating to any
occurrence, event or matter which has taken place, occurred or happened twenty years before the date on which any
request is made under section 6 shall be provided to any person making a request under that section:
Provided that where any question arises as to the date from which the said period of twenty years has to be
computed, the decision of the Central Government shall be final, subject to the usual appeals provided for in this Act.
you can deny that information by citing the reason in reference to sub-clause(j)of clause(1) of section 8 of RTI Act 2005.It depends upon the satisfaction of the officers(mentioned in the sub-clause(j)) in view of larger public interest. Ask the applicant how he thinks the information he seeks is of larger public interest.If his answer satisfy your wisdom(Of course not Biased one),you may give him the required information and if not you can say a big no(in good faith).