Do you need a service agreement?

You need a service agreement for any client work worth invoicing, even though no law makes one mandatory. Work without one is still governed by contract law, just with terms reconstructed later from emails and memory, which is the worst version of having a contract.

What it earns you is specific: enforceable payment terms, a scope boundary that stops free extra work, agreed ownership of the output, a liability cap, and a clean exit. Every one of those is a live dispute somewhere right now between two people who skipped the paperwork.

Is it worth it for tiny jobs? A one-hour favor, maybe not. Anything recurring, anything above a few hundred dollars, anything with deliverables a client could reject: yes. It takes minutes and removes the expensive ambiguity.

This client service contract template is the standing version you reuse for every engagement.