Surety Bond vs Letter of Credit

Surety bonds and letters of credit can both serve as financial security on a construction project. Both protect the owner against contractor default. Both involve a third-party institution standing behind the contractor’s obligation. From the owner’s perspective the two instruments cover similar ground in similar ways. From the contractor’s perspective they are very different products with very different operational implications.

A surety bond is a three-party instrument issued by a surety company. The surety pays the obligee if the principal defaults, and then pursues the principal under the indemnity agreement. The surety underwrites continuously and treats the bond as exposure within the contractor’s overall capacity allocation rather than as a separate transaction.

A letter of credit (LC) is a bank-issued instrument that obligates the issuing bank to pay the beneficiary on demand or on the satisfaction of specific documentary conditions. The LC is backed by collateral the contractor has pledged to the bank, typically cash, securities, or borrowing capacity under the contractor’s credit facility. The bank’s exposure is fully secured; the LC functions more like a parked deposit than like a credit underwriting.

Most public construction in the United States requires surety bonds rather than letters of credit. The Miller Act and the Little Miller Acts specify performance and payment bonds; LCs are generally not an acceptable substitute on public work because they do not provide the payment-bond protection to subcontractors and suppliers that the statutes require.

Public-work alternatives are narrow

Some federal procurement allows alternative bid guarantees (cashier’s checks, irrevocable LCs, or cash deposits) at the bid stage, under limited circumstances spelled out in FAR Part 28. The performance and payment bonds at award are typically required as surety bonds. State and municipal Little Miller Acts vary, but the dominant pattern is surety bonds for the P&P obligation.

Private contracts have more flexibility

Private owners are not bound by the Miller Act framework and can accept whichever security the contract specifies. Some private owners explicitly allow LCs as an alternative to performance bonds. Some accept LCs only on smaller projects or under specific circumstances. Some require surety bonds across the board because the payment-bond protection benefits the project’s subcontractor and supplier relationships, not just the owner directly.

Maintenance bonds, retention release, and warranty

LCs surface most often on private work as substitutes for retention or as backstops for maintenance and warranty obligations after substantial completion. An owner releasing retention against a maintenance LC is treating the LC as the post-completion security that replaces the retention. These are narrower applications than full performance security but are common on private commercial work.

The pricing of surety bonds and letters of credit looks similar on paper (both are quoted as a percentage of the face amount) but the underlying economics are different.

Surety bond premium

Surety bond premiums are paid as a one-time premium at issuance, calculated as a percentage of the contract value, with the percentage varying by contractor classification and project type. The premium is paid once for the duration of the project. The surety’s capacity allocation to the bond ties up the contractor’s capacity, but does not consume working capital directly.

Letter of credit fees

LC fees are typically charged as an annual percentage of the LC face amount, often in the 1% to 2% range, with substantial variation by bank and by collateral arrangement. Unlike a surety bond premium, the LC fee accrues annually, so a multi-year project pays the fee multiple times. On a long-duration project, the cumulative fee can substantially exceed the equivalent surety bond premium even if the per-year rate looks competitive.

The collateral cost

The bigger cost difference is the collateral. An LC requires the contractor to pledge collateral to the bank, typically by drawing down or restricting borrowing capacity under the firm’s credit facility. The pledged collateral is unavailable for working capital, for other LCs, or for any other use during the LC’s tenure. On a $5 million performance LC tying up $5 million of borrowing capacity for two years, the opportunity cost of the unavailable working capital often exceeds the LC fee itself.

No collateral on a surety bond

A surety bond does not require collateral in the same way. The surety underwrites the contractor and the bond exposure based on the indemnity agreement, not against pledged assets. The contractor’s working capital remains available for operations. This is the structural advantage of surety bonds over LCs from the contractor’s perspective.

The two instruments behave very differently when a claim is made. The difference matters both for the contractor (which has the indemnity exposure) and for the owner (which has different recovery dynamics).

Surety bond: investigation, then resolution

When a performance bond is called, the surety investigates before paying. The surety may complete the work through a takeover, indemnify the owner, or pay out the bond, depending on the circumstances of the default. The investigation can take weeks or months. The owner does not get immediate cash; the owner gets the surety’s engagement on resolution, which can be more valuable but takes longer to materialize.

Letter of credit: pay on demand

An LC pays on demand, or on satisfaction of the documentary conditions specified in the LC. The bank does not investigate the underlying dispute between the contractor and the owner. If the owner presents the documents required by the LC, the bank pays. The contractor’s only recourse against an improper draw is litigation against the owner after the fact, which is meaningfully harder than litigating before the bank pays out.

The owner’s perspective

From the owner’s perspective, the LC is more powerful in some respects (immediate payment, no investigation) and weaker in others (no payment-bond protection for subcontractors and suppliers, no surety engagement on completion). Owners that want fast cash recovery prefer LCs. Owners that want a partner in resolving project problems prefer surety bonds. Most large institutional owners have settled on bonds for performance security and accept LCs only for narrow secondary purposes.

The contractor’s perspective

From the contractor’s perspective, surety bonds are operationally preferred when both options are available. The working capital efficiency, the lower cumulative cost on multi-year work, the surety’s engagement during disputes (sometimes helpful to the contractor as well as the owner), and the avoidance of pay-on-demand exposure all favor bonds. LCs make sense when the contractor’s surety relationship is constrained, when the owner specifically requires an LC, or when the project is small enough that the working capital cost is manageable.

On most procurement, the contract specifies what the owner wants and the contractor either provides it or does not pursue the work. The choice between surety and LC is largely the owner’s, made before the contractor sees the solicitation. But there are situations where the contractor has options or can negotiate.

On private commercial work where the contract is being negotiated, contractors with strong surety relationships sometimes propose surety bonds as an alternative to LCs the owner has initially specified. The argument is straightforward: the owner gets the same level of protection at lower friction for the contractor, which can support more competitive pricing. Some owners accept the substitution; others require LCs for reasons specific to the owner’s preferences or financing structure.

On work where retention is being released against post-completion security, the contractor sometimes has the choice between a maintenance bond and a maintenance LC. The maintenance bond is typically more efficient for the contractor for the same reasons surety bonds generally beat LCs on working capital. The owner’s contract or the practical realities of the post-completion period determine whether the substitution is workable.

On covered procurement, the bond requirements (whichever instrument the owner has specified) flow through the solicitation as specific clauses, specific forms, and specific timing. The ScalaBid Submission Package surfaces the security requirements in the action checklist, regardless of whether the requirement is a surety bond, an LC, or any other form. The contractor takes the checklist to the producer or to the bank with the lead time the relationship needs, rather than discovering the security requirement at the end of a bid window when the rest of the response is otherwise ready to submit.