As per section 154
(7) Save as otherwise provided in section 155 or sub-section (4) of section 186 no amendment under this section shall be made after the expiry of four years98[from the end of the financial year in which the order99 sought to be amended was passed.]
(8) Without prejudice to the provisions of sub-section (7), where an application for amendment under this section is made by the assessee on or after the 1st day of June, 2001 to an income-tax authority referred to in sub-section (1), the authority shall pass an order, within a period of six months from the end of the month in which the application is received by it,—
(a) making the amendment; or
(b) refusing to allow the claim.
So application can be made within 4 years and order should be passed within 6 months of the application.
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