Investments to be shown in Income Tax Returns

Interest on RD, NSC and other deposits would be your income from other sources which needs to disclosed in the ITR. You may claim deduction u/s 80C (NSC interest except for last year and 5-yr deposit) and on interest income u/s 80TTB if you are a senior citizen.

You have already mentioned that the source of income is savings. When you initially earned those savings, you would have paid tax on it. So you don't have to pay tax on it again. In other words, tax is paid on the interest earned on deposits (not on deposits itself).