The Form 15G/H needs to be submitted at the beginning of every financial year or at the time of deposit if in case the investment is done during financial year. In case of entities/companies the Lower tax deduction certificate needs to be submitted immediately after the date of issue or before 31st Mar (financial year end) whichever is earlier.
Note:- Form 15G/H is not applicable for cases wherein the deposit interest exceeds the tax exemption limit set by the income tax department. i.e Rs.2.5 lacs for individuals & Rs.3 lacs for senior citizens OR as applicable time to time.