Co-sourcing

Co-sourcing is a delivery model where an in-house team and an external provider run one function together and split the work between them. The client keeps ownership and direction while the provider supplies the capacity or specialist skill the internal team lacks.

It sits in the middle of the sourcing scale. On one side you keep everything in-house and carry the full cost of hiring. On the other you hand a whole function to a vendor and buy an outcome.

Co-sourcing refuses both extremes. Your people stay in charge of priorities, standards and reporting. The partner plugs into your workflow, works to your plan, and scales up or down as demand shifts.

That middle position is why regulated and judgement-heavy functions like it. You get outside skill without giving up the internal knowledge, relationships and accountability that a full handover tends to erode.

Key takeaways

• Co-sourcing splits one function between your staff and a provider, rather than moving the whole function out.
• You keep the plan — the priorities and the reporting line; the provider brings capacity or niche skill.
• Internal audit is the clearest established use case, with published professional guidance behind it.
• It suits work that needs deep company context plus specialist expertise you can’t justify hiring full-time.
• It differs from fully managed outsourcing, where the provider owns the outcome, not just the effort.

How it works

Co-sourcing works by mapping your plan against your team’s real capabilities, finding the gaps, then buying only those gaps from a partner. Your staff and theirs work the same queue under one set of standards, with your leadership still accountable for results.

The internal audit version shows the mechanics well. Accounting Today’s write-up of guidance from the Institute of Internal Auditors describes a chief audit executive (CAE) who assesses the audit plan and staff capabilities to identify gaps.

The CAE then matches existing staff skill sets against the audits the plan actually calls for. Whatever the team can’t cover becomes the shortlist for a partner.

Governance stays put. The audit committee reviews the appropriateness and expertise of the resources as part of the annual audit plan.

Two hard rules apply in that setting. Any provider considered for internal-audit co-sourcing must be independent of the organisation’s external auditors.

And the CAE must keep reporting to executive management and the audit committee on all activities, regardless of how they’re sourced.

The Institute of Internal Auditors has also published a position paper, “Resourcing Alternatives for the Internal Audit Function”, covering the choice between models.

Here’s how the three sourcing shapes compare:

Compare that with fully managed outsourcing, where the provider takes the whole result, and with traditional outsourcing, which usually moves defined tasks out wholesale.

Examples

Co-sourcing turns up wherever a function needs deep internal context plus a skill that’s too narrow or too expensive to keep on payroll year-round. Audit, technical delivery and analytics teams use it most often, and the pattern repeats across industries.

Internal audit. A mid-size bank keeps its own audit team for routine controls testing, then brings in a specialist firm for cyber or treasury audits.

Both teams work to one rulebook. The Global Internal Audit Standards, 2024 Edition, known as The Redbook, is built on 15 principles.

Each principle is supported by standards carrying requirements, implementation considerations and examples of evidence of conformance.

Technology delivery. A retailer’s in-house engineers own the product roadmap while an offshore partner supplies extra developers for a fixed release window. The roadmap never leaves the building.

Analytics and research. A healthcare group keeps its analysts close to clinical staff, then co-sources statistical modelling for a specific study. This is close to knowledge process outsourcing, except the internal team stays hands-on throughout.

Customer support surge. A subscription business runs tier-one support internally and adds partner agents for a seasonal peak, using shared scripts and one quality scorecard.

Sourcing analysts such as Everest Group publish ongoing commentary on how these model choices play out.

Location choices sit on top of the model. Teams pair co-sourcing with offshore outsourcing for cost, nearshore outsourcing for timezone overlap, or onshore outsourcing where data rules bite.

Related terms

Co-sourcing sits inside a family of sourcing models that differ mainly on who owns the outcome, who employs the staff and where the work physically sits. These related terms help you place it precisely against the alternatives buyers usually shortlist.

• Fully Managed Outsourcing: a model where the provider owns the outcome end to end.
• Traditional Outsourcing: the long-standing practice of moving defined tasks or processes to a vendor.
• Managed Services: ongoing delivery of a function against agreed service levels rather than per-project work.
• Captive Center: a wholly owned offshore site staffed by your own employees.
• Business Process Outsourcing (BPO): the contracting of complete business processes to an external provider.
• Outsourcing Consultants: advisers who help buyers pick, scope and negotiate a sourcing model.

FAQ

What’s the difference between co-sourcing and outsourcing?

Co-sourcing keeps your team doing part of the work and holding the plan, while the provider fills specific gaps. Full outsourcing hands the function, and usually the accountability, to the vendor.

Is co-sourcing only used for internal audit?

No — audit is simply the clearest documented case, with professional guidance behind it. The same split-the-work pattern shows up in technology delivery, analytics, finance operations and customer support.

Who is accountable in a co-sourcing arrangement?

You are. In internal audit — the chief audit executive must keep reporting to executive management and the audit committee on all activities, no matter how they’re sourced.

Can a co-sourcing partner also be our external auditor?

No. Guidance covered by Accounting Today states that any provider considered for internal-audit co-sourcing must be independent of the organisation’s external auditors.

When should we choose co-sourcing over hiring?

Choose it when the skill you need is genuinely specialist or temporary, and the context around the work is too company-specific to hand over completely.

Browse the Outsource Accelerator directory to compare providers that support co-sourced delivery models.