A co-surety is one of two or more parties who guarantee the same obligation of the same principal debtor to the same creditor. Each co-surety stands on equal legal footing with the others, and each carries a share of the risk that the principal will default. The arrangement shows up most often in construction bonding, federal contracting, and large commercial loans, where the exposure is too big or too concentrated for a single guarantor to absorb comfortably.
Co-Surety vs. Sub-Surety
The defining feature of co-suretyship is horizontal equality. Each co-surety occupies the same tier of liability toward the creditor and guarantees the principal’s obligation directly. A sub-surety is different: a sub-surety guarantees the performance of another surety rather than the principal. If Surety A and Surety B both back a contractor’s performance bond for the same project owner, they are co-sureties. If Surety C instead guarantees that Surety A will honor its bond, Surety C is a sub-surety.
Co-sureties do not have to sign the same document, and they do not have to know about each other when they become bound. What matters is that they are each obligated for the same debt. Courts have held that even when signers appear as principals on the face of an instrument, parol evidence can establish that some were actually co-sureties, and the right of contribution follows from that finding.
Why Co-Sureties Get Used
The most common trigger is a federal underwriting cap. Under Treasury regulations, no surety company holding a certificate of authority from the Treasury Department may underwrite a single risk exceeding 10 percent of its paid-up capital and surplus.1eCFR. 31 CFR 223.10 – Limitation of Risk When a bond’s face amount exceeds that limit, the excess has to be covered through co-insurance, reinsurance, or both.2Bureau of the Fiscal Service. Department Circular 570
The Federal Acquisition Regulation puts this into practice. If a bond’s penal sum exceeds the surety’s underwriting limit listed in Treasury Department Circular 570, the bond is acceptable only if the excess is coinsured or reinsured, with no coinsurer or reinsurer taking on more than its own underwriting limit. Reinsurance agreements generally have to be executed and submitted with the bonds before the contracting officer makes a final determination.3Acquisition.gov. FAR 28.202 – Acceptability of Corporate Sureties
Co-suretyship also arises voluntarily. A creditor facing a very large exposure may insist on multiple sureties. And a surety may prefer to split a bond rather than concentrate that much liability on its own books, even when its underwriting limit would technically allow the full amount.
How Liability Works Toward the Creditor
Unless the bond says otherwise, co-sureties are jointly and severally liable to the creditor. That means the creditor can pursue any single co-surety for the full amount, regardless of how many others exist. The creditor does not have to chase proportional shares or wait for one surety to refuse before turning to another.
The alternative is a limited co-suretyship, where the bond specifies a dollar cap or percentage for each surety. Under that structure, no co-surety is responsible for more than its stated portion, even if the others default. The tradeoff is straightforward. Joint and several liability gives the creditor maximum flexibility; limited co-suretyship gives each surety a hard ceiling. The bond has to say so clearly. Silence almost always defaults to joint and several liability.
Contribution Between Co-Sureties
The creditor’s ability to collect the full amount from any single co-surety would be unfair if it ended there. It does not. The right of contribution governs the internal relationship among co-sureties: if one pays more than its fair share, it can demand reimbursement from the others.
Under the Restatement (Third) of Suretyship and Guaranty, each co-surety’s contributive share is calculated by dividing the aggregate liability by the number of co-sureties. Three co-sureties on a $900,000 bond each carry a $300,000 share. If Surety A pays the full $900,000, Surety A can demand $300,000 from Surety B and $300,000 from Surety C.
The math changes when a co-surety has a capped guarantee. If Surety C’s bond limits its liability to $100,000, that cap comes off the top and the remaining $800,000 splits between A and B at $400,000 each. Any express agreement among the co-sureties about how to divide the burden overrides the default equal-share rule.
When a Co-Surety Cannot Pay
An insolvent co-surety’s share does not disappear. It is redistributed among the remaining solvent co-sureties as if the insolvent party had never been part of the arrangement. Each surviving co-surety’s share goes up accordingly.
The Restatement addresses this directly. When contribution from one co-surety falls short due to insolvency, lack of personal jurisdiction, or similar circumstances despite reasonable collection efforts, the shares of the remaining co-sureties are recalculated as though the shortfall party’s obligation was limited to whatever was actually recovered. If nothing was recovered, the others absorb the entire gap. This is one of the underappreciated risks of co-suretyship: you are exposed not only to the principal’s default but also to the financial health of your fellow sureties.
Recovering From the Principal
Contribution reaches fellow co-sureties. Subrogation reaches the principal itself. After paying the creditor, the paying surety steps into the creditor’s shoes and can pursue the principal for the full amount paid, using the same rights and remedies the creditor originally had. That includes going after any collateral the principal pledged to secure the underlying obligation.
The two remedies serve different functions and reach different pockets. A co-surety who has paid the entire bond amount usually pursues subrogation against the principal first, because that is where the obligation started. If the principal has no assets or has filed for bankruptcy, contribution claims against the other co-sureties handle whatever loss remains.
Defenses That Can Discharge a Co-Surety
Co-sureties are not defenseless when the creditor behaves badly. Several actions by the creditor can partially or fully discharge a co-surety’s obligation:
- Release of the principal. If the creditor releases the principal debtor from the underlying obligation, co-sureties are discharged to the extent of that release. A guarantor cannot be held responsible for a debt the creditor has forgiven.
- Material modification. If the creditor and principal materially change the terms of the underlying contract without the co-sureties’ consent, the co-sureties may be discharged to the extent the change increases their risk.
- Impairment of collateral. If the creditor negligently loses, releases, or damages collateral securing the obligation, co-sureties are discharged to the extent of that impairment.
- Release of a co-surety. Traditional common law discharged all co-sureties when the creditor released one without reserving rights against the others. Modern law has softened the rule, but releasing one co-surety still affects the others by shrinking their contribution rights. The remaining co-sureties are generally discharged to the extent they are harmed by losing contribution against the released party.
There is a catch. Most modern surety bonds and indemnity agreements contain broad waiver clauses in which the co-sureties consent in advance to modifications, extensions of time, releases of collateral, and similar creditor actions that would otherwise trigger a discharge. Courts generally enforce these waivers when the language is clear. In practice, a co-surety’s defenses are often much narrower than the common law defaults would suggest. Read the waiver language before signing.
The Indemnity Agreement Behind the Bond
Before issuing a bond, most surety companies require the principal and any co-sureties to sign a general indemnity agreement. This is where much of the real financial exposure lives, and the obligations reach beyond the bond itself.
A typical indemnity agreement contains a hold-harmless clause requiring the indemnitors to reimburse the surety for every claim, liability, legal fee, and expense the surety incurs from issuing the bond. It also contains a collateral security provision letting the surety demand cash deposits whenever it believes a loss is likely, often in an amount the surety determines at its sole discretion. The indemnitors owe as soon as liability is asserted against the surety, not just after the surety has actually paid a claim.
When co-sureties or reinsurers are involved, the indemnity agreement usually extends its protections to all of them. Standard industry language provides that if the surety executes bonds with co-sureties or reinsures any portion, the terms of the indemnity agreement apply for the benefit of those co-sureties and reinsurers according to their respective interests. The principal’s indemnity obligations run to every co-surety on the bond, not only the lead.