Different public sector entities (Government companies) offer different interest rates for tax-free bonds. The returns also differ for different projects. It is better to check, compare and choose the higher ones for the same tenure (investment duration).
For any tax-free bond, the purpose of the investment will be clearly stated in the information document. If no purpose is given for an investment, that might be a fraud!
Beware of fraud Ponzi schemes. Read more here.
Investment in Tax-free bonds is for a very long term. Make sure you are not putting all your money in tax-free bonds. Keep an adequate amount of money in shorter-term deposits as well.
Keep some amount of your savings in your savings bank account for emergencies. Don’t put all your savings into investments.