Duplication is normal, and mostly invisible
A household with a car, a home policy, a bank account carrying incidental benefits and a credit card with purchase protection is very likely to hold several overlapping promises without having chosen any of them deliberately. Legal expenses cover appears in three or four places. Breakdown assistance is bundled into vehicles, cards and packaged accounts. Personal effects sit in both motor and contents wordings.
Nobody set out to buy the same thing twice. Cover accumulates because it is cheap to bundle, and because a product that includes an extra looks better than one that does not. The result is that after a loss there is often more than one place to turn, and no obvious way to know that.
Indemnity sets a ceiling on the whole thing
The governing idea is that insurance restores a position rather than improving one, so a person cannot recover more than the loss they actually suffered no matter how many policies could respond. Claiming the same repair from two insurers is not clever arbitrage. It is a fraud, and it is the kind that is detected easily because insurers share claims data.
What the second policy does instead is stand behind the first. If one insurer pays, the other has no further liability for that loss, and where both are on risk they arrange the split between them. The insured is kept whole once.
The other insurance clause decides who goes first
Most wordings contain a clause dealing with the situation directly. Some say the policy will pay only its rateable proportion where other cover exists, which means each insurer contributes in proportion to what it was on risk for. Others say the policy will not respond at all if other insurance is available, making it an excess layer sitting above the first.
When two policies both claim to be the excess layer, the clauses cancel each other out under the law of several jurisdictions and the insurers contribute anyway. That argument happens between them, usually without troubling the policyholder. It is nonetheless the reason a claim can sit unexplained for weeks while nobody appears to be doing anything.
Fixed benefits are the exception that genuinely stacks
Contribution applies to indemnity cover, where a measurable loss is being restored. It does not apply in the same way to promises to pay a stated sum on a defined event, because there is no loss to measure and therefore nothing to duplicate in the legal sense. Accident benefits of that kind can generally be claimed alongside anything else.
The same logic explains why a payment for injury and a payment for a damaged car do not offset each other: they are compensating different things. The rule is about not being paid twice for one loss, not about being paid only once in total.
What duplication actually buys
Choice is the honest answer. Two possible routes mean an option about which excess to bear, which record to mark, and which claims process to endure, and those are real differences even though the money at the end is the same. A legal expenses insurer that will fund a case is worth having whether or not another one exists.
Speed sometimes matters too. Where one policy responds immediately and another requires a liability decision first, the faster one gets the car repaired and sorts out the money afterwards. But paying twice for the same promise with no such advantage is simply a cost, and a packaged account or a card benefit frequently duplicates something already bought deliberately.
Finding the overlaps before a loss rather than during one
The practical exercise takes an evening and is done once. List the policies, the accounts and the cards, then note against each what it says about legal expenses, breakdown, personal possessions away from home, travel and accident benefits. Most people find at least one duplicate and at least one gap they assumed was covered.
Two cautions apply. Bundled benefits attached to accounts and cards change without much notice, so a note made two years ago may describe a benefit that has since been withdrawn. And every one of these products is governed by its own wording in its own market, so what a clause does where you live has to be read there rather than inferred from a general description.
