The question of what to send is usually asked without the mirror question, which is what to keep and why. Some of the answers are obvious and two of them are not.
Work where the context changes faster than it can be written
If the right answer this week differs from last week's for reasons nobody has articulated, no handover survives. That is not a statement about distance; a new local employee would struggle equally, and you would notice sooner because they sit near you.
Where the volatility is genuine, keep the work. Where it is simply undocumented, the work is a documentation problem rather than a location one, and the documentation is worth doing regardless.
Work with a long feedback loop
Anything whose quality only becomes visible weeks later is hard to supervise at any distance and harder across a time zone. The person producing it gets no signal, and the first signal anybody gets is a problem.
Either keep it, or invest in an interim check that produces feedback in days rather than months. Frequently the interim check is worth building whether or not the work moves.
Work where accountability is personal and local
Some obligations attach to a named individual in a particular jurisdiction: signing accounts, holding a licence, certifying compliance. The work supporting those obligations can move; the obligation cannot.
Keeping the two straight is a legal question rather than an operational one and it should be asked of an adviser rather than a provider.
The capability to do it yourself
Here is the one businesses skip. If every person who understands a process is outside your organisation, you have transferred the process and the knowledge of it, and your ability to change providers, bring the work back or even specify it properly has gone with them.
Keep at least one person who could do the work, or who has done it recently enough to review it critically. That person is not overhead; they are what makes the arrangement reversible.
The person who writes the briefs
The second one businesses skip, and the more important of the two. The whole arrangement rests on somebody being able to describe work clearly and judge whether it came back right.
That capability is rare, it is not the same as being senior, and it is the single largest predictor of whether an offshore team produces anything. Identify who has it before you hire anybody, and protect their time, because it is the input the model in the entry on cost is consuming.
What can safely move that people assume cannot
Customer contact, in many cases. Voice roles, support and appointment setting are done well from here for clients in several countries, and the objections raised are usually about accent and turn out on inspection to be about training and about how much context the person was given.
Anything involving confidential data, provided the controls exist. The controls are the question, not the geography, and the entry on the bookkeeping role sets out what they look like.
The concentration risk
Even where everything is written down, a team of six who all know a process and all work for the same provider in the same building is a concentration. It is not an argument against the arrangement; it is an argument for knowing it exists, keeping the documentation on your own systems, and having considered what a transition would involve before you need one.
A short test
For each candidate task, ask what happens if the person doing it disappears on Monday. If the answer is that somebody follows a document, the work can move. If the answer is that somebody spends a fortnight working out what they were doing, keep it and fix that first.
The documentation stays with you
Procedures written during a handover should live on your systems, in your account, under your control. Where they live in a provider's knowledge base, changing provider means rewriting them.
This costs nothing to arrange at the start and is awkward to retrofit, which is a description that fits several things in this part.
What a reversible arrangement looks like
Documentation on your systems. At least one person onshore who could do or review the work. Access under accounts you own rather than the provider's. And an idea, written down, of what bringing the work back would take.
None of that implies distrust. It is the same discipline that applies to any single supplier of anything, and the fact that this supplier employs people rather than shipping goods does not change it.
The question about your own systems
Whether your tools support named accounts with scoped permissions for external staff. Where they do not, the choice is between granting more access than you should and not moving the work, and discovering that after signing is a poor sequence.
Which obligations must be discharged by a person in a particular jurisdiction, and what may be delegated or performed elsewhere, is a question of the law where the obligation arises. This entry describes the general shape of the distinction and nothing in it is legal advice about any obligation of yours.