Subrogation is the legal doctrine whereby one person takes over the rights or remedies of another against a third party. Rights of subrogation can arise two different ways: either automatically as a matter of law, or by agreement as part of a contract. Subrogation by contract most commonly arises in contracts of insurance. Subrogation as a matter of law is an equitable doctrine, and forms part of a wider body of law known as unjust enrichment. The two most common areas where subrogation is relevant are insurance and sureties. In each case, the basic premise is that where one person (i.e. typically an insurer or a guarantor) makes a payment on an obligation which, in law, is the primary responsibility of another party, then the person making the payment is subrogated to the claims of the person to whom they made the payment with respect to any claims or remedies which are exercisable against the primarily responsible party. For example, if a car owner has collision insurance  on their car and the car is damaged by a negligent third party, if the car owner elects to claim under his insurance policy, then any claims which the car owner had against the negligent party will pass to the insurance company in countries which recognise the doctrine. Similarly, if a father guarantees the debts of his son to the bank (i.e. a contract of suretyship), and the bank elects to call upon the guarantee rather than claiming against the son directly, then if the father pays out on the guarantee, he will become subrogated to the bank's claims against the son.
The doctrine of subrogation can also pass proprietary rights, i.e. a security interest or claim to ownership of goods. If a work of art is stolen, and the insurance company pays out under a policy of insurance to the owner, if the art is later recovered, then legally it will belong the insurance company under rights of subrogation. Similarly, if a ship is insured and then sinks, any rights of salve will pass to the insurer if the claim is paid out as a total loss. If a guarantee is paid out by a guarantor, but the bank also held a mortgage over the debtor's home, then the guarantor will be subrogated to the bank's rights as a mortgagee with respect to the debtor's home.
In the most common areas where subrogation arises as a matter of law, it will also commonly be regulated in the terms of the relevant contract. For example, in a contract of guarantee, the guarantee will often provide that the guarantor either waives their right of subrogation, or agrees not to exercise it unless the bank has completely been paid in full. In a contract of insurance, in addition to right of subrogation at law, there will often be a contractual right of subrogation which will be bolstered by the insured party agreeing that they will provide all necessary assistance to the insurance company in pursuing any subrogated claims.
Subrogation is sometimes misunderstood by lay people and criticised on the basis that payment under an insurance claim is simply a right based upon their payments of insurance premia, and a belief that they should also retain a right to exercise any claims arising from the insured event. However, an insurance contract is a contract of indemnity, and to allow a party to receive insurance proceeds and claim against third parties would mean that they might recover more than their total loss. Because subrogation operates to prevent such over-recovery, it is considered to form part of the general law of unjust enrichment (i.e. preventing a party by being unjustly enriched by pursuing a claim for a loss in respect of which they have already been indemnified).
Subrogation is an equitable remedy and is subject to all the usual limitations that apply to equitable remedies.
Although the basic concept is relatively straightforward, subrogation is considered[by whom?] to be a highly technical area of the law.
Types of subrogation 
Although the classes of subrogation rights are not fixed (or closed), and vary between different legal jurisdictions, types of subrogation are commonly divided into the following categories:
- Indemnity insurer's subrogation rights
- Surety's subrogation rights
- Subrogation rights of business creditors
- Lender's subrogation rights
- Banker's subrogation rights
- Trustee's subrogation rights
Although the various fields have the same conceptual underpinnings, there are subtle distinctions between them in relation to the application of the law of subrogation.
Indemnity insurer's subrogation rights 
With insurance subrogation, there are three parties involved: the insured; the insurer; and the tortfeasor (the party who is responsible for the damages). Under subrogation, the insurance company assumes the right to sue the tortfeasor for the amount of the damages reimbursed to the insured. An indemnity insurer has two distinct types of subrogation rights. Firstly, they have the classic type of subrogation used in the example above; viz. the insurer is entitled to take over the remedies of the insured against another party in order to recover the sums paid out by the insurer to the insured and by which the insured would otherwise be overcompensated. Secondly, the insurer is entitled to recover from the insured up to the amount which the insurer has paid to the insured and by which the insured is overcompensated. The latter situation might arise if, for example, an insured claimed in full under the policy, but then started proceedings anyhow against the tortfeasor, and recovered substantial damages.
Surety's subrogation rights 
A surety who pays off the debts of another party is subrogated to the creditor's former claims and remedies against the debtor to recover the sum paid. This would include the endorser on a bill of exchange.
In relation to a surety's subrogation rights, the surety will also have the benefit of any security interest in favour of the creditor for the original debt. Conceptually this is an important point, as the subrogee will take the subrogor's security rights by operation of law, even if the subrogee had been unaware of them. Accordingly, in this area of the law at least, it is conceptually improbable that the right of subrogation is based upon any implied term.
Subrogation rights against trustees 
A trustee of a trust who enters into transactions for the benefit of the beneficiaries of the trust is generally entitled to be indemnified by the beneficiaries for personal loss incurred, and has lien over the trust assets to secure compensation. If, for example, the trustee conducts business on behalf of the trust and fails to pay creditors, then the creditors are entitled to be subrogated to the personal and proprietary remedies of the trustee against the beneficiaries and the trust fund. Where under the terms of the trust instrument the trustees are permitted to trade in derivatives as part of the trust's investment strategy, then the derivatives document will also normally contain a subrogation clause to bolster the common law rights.
Lender's subrogation rights 
Where a lender lends money to a borrower to discharge the borrower's debt to a third party (or which the lender pays directly to the third party to discharge the debt), the lender is subrogated to the third party's former remedies against the borrower to the extent of the debt discharged.
However, if the original loan was invalid (because, for example, it was ultra vires the borrower) then the lender generally cannot enforce the third party's claim against the borrower as this would indirectly validate an invalid loan. Nonetheless the claim can subsist insofar as the unlawfully borrowed money was used to discharge lawful debts, by inferring the legality of the use of the funds to the right of subrogation. The law in this area has been subject to conflicting decisions.
Banker's subrogation rights 
Where a bank, acting on what it believes erroneously to be the valid mandate of its client, pays money to a third party which discharges the customer's liability to the third party, the bank is subrogated to the third party's former remedies against the customer.
In Lord Napier & Etterick v Hunter  2 WLR 42, the House of Lords confirmed that an (indemnity) insurer's subrogation rights dictate that in a claim against the assured (for damages personally recovered by the assured) the insurer is not limited to a simple personal remedy; the insurer also has the benefit of an equitable lien over the damages received by the assured in respect of the insured loss. That case also controversially held that in working out the compensation to which the insurer is entitled the assured cannot be said to have first recovered the whole of his uninsured loss, and must instead be considered to have owed foremost the excess agreed.
Subrogation can thus in rare instances deprive the consumer of the benefit of the Make Whole Doctrine, the right of an injured party to recover full damages. This abrogation of Make Whole doctrine puts the insurer in the position of having first claim to an at-fault party's assets, even if the assured is left with reduced damages from the insurer as a result (see Northern Buckeye vs Lawson - 2004). In other words, the law's intent to prevent dual recovery by the assured can lead to less-than-equitable recovery (see Roger Baron).
In the cited case, the Ohio Supreme Court ruled that the language of the assured's insurance contract overruled Ohio's statutory default Make-Whole Doctrine. For this reason, an insured client needs a full awareness of subrogation clauses in their insurance contracts, including insurance provided by employers, fraternal organizations, etc.
- "What is SUBROGATION?". Retrieved 2013-01-31.
- "Legal definition of subrogation". thefreedictionary.com. Retrieved 2013-01-31.
- "Subrogation and Insurance Claims". Adjusting Today.
- Mason v Sainsbury (1782) 3 Dougl KB 61; Morris v Ford Motor Co  QB 792
- Castellain v Preston (1883) 11 QBD 380; Re Miller, Gibb & Co  1 WLR 703
- In practice there are many reasons why an insured may do this; to recover a related uninsurable loss, to establish a defence to other claims against the insured. However, in each case the law requires them to return the amount of any compensation received in respect of which they have also received insurance payments to the insurer.
- Forbes v Jackson (1882) 19 Ch D 615
- Duncan, Fox & Co v North and South Wales Bank (1880) 6 App Cas 1
- Charles Mitchell, The Law of Subrogation, ISBN 0-19-825938-7
- Re Johnson (1880) 15 Ch D 548; Re Oxley  1 Ch 604
- In most jurisdictions the trustees would be prohibited from such risky investments by law unless expressly empowered by the trust instrument.
- Butler v Rice  2 Ch 277; Ghana Commercial Bank v Chandiram  AC 732
- Sinclair v Brougham  AC 398; much criticised on this point.
- Orakpo v Manson Investments Ltd  95, per Lord Goff
- For example, in Nottingham Permanent Benefit Building Society v Thurstan  AC 6 the House of Lords held that a building society could be subrogated to an unpaid vendor's lien in respect of an unlawful loan to an infant to purchase land.
- B Liggett (Liverpool) Ltd v Barclays Bank Ltd  1 KB 48