Ask agencies who tried offshore delivery and stopped why it did not work, and most will say quality. Push one level and it is almost never that the work was beyond the team. It is that nobody looked at it before the client did.
Where Offshore Delivery Actually Fails
The failure is structural, not personal. When work is produced in the same room, review happens informally. Someone glances at a screen, a question gets asked in passing, a mistake gets caught before it ships.
Move production to a different time zone and all of that informal checking disappears. If you did not deliberately replace it, you did not move the work. You removed the safety net from it.
An agency that sends unreviewed offshore work to a client is not saving money. It is deferring a churn event, and the cost of that event is the annual value of the account, which is always larger than the rate saving.
Who the Reviewer Has to Be
Three properties, and all three are required.
They know what this client expects. Not general standards, this client. Brand rules, tone, the thing the client complained about in March. Generic QA catches typos and misses the thing that actually loses accounts.
They can send work back. If the reviewer cannot delay a deliverable, they are a commentator. Authority has to come with the role or reviews become a formality that everyone learns to pass.
They are measured on quality, not throughput. A reviewer whose target is turnaround will approve things. This is the one agencies get wrong most often, usually by giving the review job to the person also responsible for delivery deadlines.
Where that person sits matters far less than whether they exist. In-house, at the partner, or split. What matters is that the role is real.
What the Review Checks
Useful reviews check three things in order, and stop at the first failure.
Did it do the job. Against the brief objective, not against whether it looks finished. Well-executed work that answered the wrong question is the most expensive failure mode, because it consumed a full cycle.
Would this client accept it. Their standards, not yours or the industry's.
Is it technically correct. Links, segments, exclusions, tracking, spelling. Last, because it is the cheapest to fix and the least likely to lose an account.
Most QA checklists run that order backwards, which is why they catch typos and miss strategy failures.
The Question to Ask Any Partner
Not what does a seat cost. Ask: who reviews the work before it reaches my client, what are they measured on, and what happens when it is not good enough.
A partner with a real review layer answers immediately and specifically, because it is a named role with a defined process. A partner without one answers with reassurance about their team being experienced.
Follow up with: show me a piece of work that failed review, and what happened next. Anyone running a genuine review process has examples. Anyone who does not will change the subject.
If You Are Building It Yourself
Budget for it explicitly. The most common mistake is modelling offshore savings on production cost alone, then discovering review has quietly become 20 to 30 percent of a senior person week, unbudgeted and resented.
Start with review on everything, then relax it by category as the team proves itself. Reversing that order teaches you which categories needed review by losing accounts in them.
And track the rework rate by category. Categories with persistent rework almost always trace back to briefs that were incomplete, which is a problem on your side, not theirs.
Part of: The GCC Model for Marketing Agencies, covering how agencies get offshore economics without building a center.