Is it permissible to subscribe to an insurance company to which one pays an annual sum for 15 years, and then receives a fixed monthly salary for 20 years or a lump sum greater than what was paid?

What has been mentioned is a form of forbidden commercial insurance, based on usury (riba) and gharar (excessive uncertainty). The aspect of usury in it is that the transaction involves present cash for deferred cash with an increase, thus containing both riba al-fadl (usury of surplus) and riba an-nasi'ah (usury of delay). There is no justification for obtaining profit or increase except in a legitimate investment contract, with conditions, the most important of which are: knowing the field of investment, the profit being a percentage of the gross profit and not a fixed amount, and it is impermissible for profits to be a percentage of the capital, or for the capital to be guaranteed to the investor. All of these conditions are not met in the matter mentioned.