Form 15H is a declaration for Indian senior citizens (60 years and above) to prevent tax deduction at source (TDS) on interest income. It is used when their total income for the financial year is below the basic exemption limit. It must be submitted annually at the start of the financial year or when making a new deposit. It declares that the individual’s income is below the taxable limits. The form is submitted online or in person, and requires the individual’s Permanent Account Number (PAN), address, and income details.