Most practices don't outsource everything at once — and shouldn't. The practices that get the most value tend to start with one clearly-bounded piece of work, prove it works, then expand. Here's a practical way to think about where to start.
The best first candidates are tasks that are repeated often, follow a consistent process, and have a clear "done" state — bookkeeping and VAT return preparation are the classic starting points for most practices. They're volume-heavy, the process is well understood, and quality is easy to check against source documents.
Work that involves direct client conversation, contentious technical judgment, or advisory input is usually better kept in-house until you've built trust in the relationship — not because it can't eventually be supported externally, but because the first few months of any new arrangement are about proving reliability on the fundamentals first.
Whatever you start with, the same questions matter: does the work arrive in a format your team can review quickly, not just a "trust us" black box? Is there a consistent point of contact rather than rotating staff? And is the provider working inside your existing software and processes, or asking you to adapt to theirs?
Outsourcing that requires you to change how your practice already works tends to create more friction than it saves. The better test is whether a new team can learn your way of doing things — the same standard you'd apply to any new hire.