Sole source

1. What is sole source?

Sole source is a contract designation under which a buyer commits to purchasing a category of goods or services from one named vendor, without competitive bidding, for the term of the agreement. It is common where a part is proprietary, a piece of equipment requires OEM-certified service, or supply continuity outweighs price competition. The designation governs procurement process, not price; the rate itself still has to be defined and matched against the invoice.

Sole source differs from a preferred vendor list, where alternates remain available even if one vendor is favored on price or service history. It also differs from a single-source situation that arose by default because only one supplier exists, rather than by a deliberate contract clause.

The distinction matters for audit purposes because a sole-source clause implies a specific written rate card and scope, while a default single-source relationship may have no such document to check the invoice against at all.

2. Why does sole source raise margin drift risk?

Margin drift is the gap between what a vendor contract says and what the invoice actually charges. Competitive bidding creates a market signal that surfaces a rate discrepancy quickly, because a buyer comparing quotes notices when one vendor's number moves out of line. A sole-source vendor faces no such comparison.

If invoice review does not check the bill against the specific rate card in the agreement, an escalation or surcharge can persist past its contracted expiration with nothing external to.

The vendor is not assumed to act in bad faith when this happens. The absence of a competing quote simply removes a check that other spend categories rely on by default, without anyone deciding to remove it.

That is why a sole-source agreement is not lower risk just because it was chosen for reliability. It is a category where the invoice has to be the check, since the market cannot perform that function here the way it does elsewhere.

3. How should a sole-source contract be reviewed?

A sole-source contract is reviewed the same way any vendor contract is reviewed: line by line against the invoice, on the same cadence as a competitively bid one. The difference is what happens if the review is skipped. Three checks matter most: that billed rates match the specific rate card in the agreement, that escalation clauses took effect on their contracted date, and that billed scope stays within what the sole-source designation actually covers.

None of these checks require renegotiating the exclusivity itself. They test whether the existing agreement is being billed as written, which is a narrower and more mechanical question than whether the vendor relationship should continue.

1. Rate card verification: Confirm invoice line items match the rate card attached to the sole-source agreement, not a general price list the vendor may also use for other customers.
2. Escalation timing: Check that any index escalation or annual increase in the contract took effect on the date specified, not earlier.
3. Scope boundary: Verify billed work falls within the scope the sole-source designation actually covers, since some agreements name a narrow category rather than the full vendor relationship.

4. Does sole source mean the vendor sets the price?

No. Sole source restricts who a buyer can purchase from during the contract term; it does not remove the contracted rate card, escalation clause, or scope boundary from that agreement. The vendor is still bound to the terms signed, and the invoice still has to match them.

What changes is the consequence of skipping the check: without a competing bid to reveal a mismatch, an unchecked sole-source invoice can carry incorrect pricing for the full contract term before anyone notices.

Ending exclusivity is one option if pricing consistently diverges from the contracted terms. Enforcing the existing contract, by matching invoices against the rate card and escalation clause directly, is a faster fix and does not require reopening the vendor relationship at all.

For the wider pattern this sits inside, start with the margin drift guide.

For the wider pattern this sits inside, start with the margin drift guide.

5. Frequently Asked Questions (People Also Ask)

What is a sole-source agreement in procurement?

A sole-source agreement is a contract clause under which a buyer agrees to purchase a category of goods or services from one named vendor for the term of the agreement, without competitive bidding. It is typically used for proprietary parts, OEM-certified service, or supply continuity.

Is sole source the same as single source?

No. Sole source is a deliberate contract clause naming one approved vendor. Single source describes a situation where only one supplier exists for a category, which can happen without any contract designation or written rate card at all.

Why does a sole-source contract need extra invoice scrutiny?

Because competitive bidding, which normally surfaces a rate mismatch when a buyer compares quotes, does not exist in a sole-source relationship. Without that external signal, invoice review against the specific rate card becomes the only check on pricing accuracy.

Can a sole-source vendor change pricing without notice?

The vendor is bound to the rate card, escalation clause, and scope defined in the signed agreement. Pricing outside those terms is a contract compliance issue to raise with the vendor, not an automatic right the sole-source designation grants them.

What should be checked first on a sole-source invoice?

Start with the rate card attached to the specific sole-source agreement, not a general price list. Then confirm any escalation clause took effect on its contracted date, and that billed scope stays within what the designation actually covers.

Does ending sole-source status fix a pricing problem?

It is one option, but enforcing the existing contract by matching invoices against the rate card and escalation clause directly is a faster fix and does not require reopening or renegotiating the vendor relationship.

How is scope defined under a sole-source clause?

Some sole-source agreements name a narrow category of work rather than the entire vendor relationship. Billed work outside that named category falls outside the sole-source designation and should be checked against separate terms or competitive pricing.

Who typically approves a sole-source designation?

Procurement or the category owner typically approves it, based on documented justification such as proprietary parts, OEM-certification requirements, or supply continuity risk. The approval governs sourcing process, not the rate itself.