Why the refund is not taxed, stated at source rather than asserted. Section 72(e) of the Internal Revenue Code governs amounts received under a life insurance contract that are not received as an annuity. Section 72(e)(5)(E)(i) applies that treatment to "any amount received, whether in a single sum or otherwise, under a contract in full discharge of the obligation under the contract which is in the nature of a refund of the consideration paid for the contract," which describes a return of premium settlement precisely. Section 72(e)(5)(A) then provides that such an amount is included in gross income "but only to the extent it exceeds the investment in the contract," and section 72(e)(6) defines the investment in the contract as the aggregate premiums paid, less any amounts already received tax-free. A refund equal to the premiums paid therefore equals the investment in the contract and leaves nothing to include. The point is worth stating carefully, because the reason the refund is untaxed is that it is the buyer's own money coming back, not that the tax code is doing the buyer a favor.
What the extra premium is buying, arithmetically. The refund is funded by the additional premium plus whatever the insurer earns on it, less the insurer's costs. So the buyer is making a long, illiquid, single-purpose savings commitment alongside the insurance, and the correct way to judge it is the implied rate of return: the annual return that would grow the extra premium into the refunded amount over the term. That number is usually low relative to what the same money could earn elsewhere, and it is not risk-free either, since it depends on the insured living, on the policy staying in force for the whole term, and on the insurer's continued ability to pay. Against that, the refund is contractually stated and, as above, generally arrives untaxed.
The conditions attached, which is where the design most often disappoints. The refund is contingent on completing the term. A policy surrendered early returns far less than the premiums paid, or nothing, and a policy that lapses for non-payment can return nothing at all, so the survival benefit is lost by exactly the households whose finances made the extra premium hardest to carry. Some contracts pay a partial refund on a stated schedule after a number of years, and that schedule is a contract term rather than a general feature. It is also worth being clear that the refund is not paid in addition to a death benefit: if the insured dies during the term, the beneficiary receives the death benefit and the premiums are not separately refunded, because the coverage did what it was bought to do.
What it is not. It is not cash value insurance. There is no account inside the contract that accumulates, can be borrowed against, or can be withdrawn from, and the surrender values that exist are a function of the refund schedule rather than of a policy account. That distinction matters because the two products are sold to the same objection and get compared to each other. The broader question of whether life insurance is a sensible place to put savings at all is a decision with its own page, and the answer there does not change because the wrapper is term rather than permanent.