They answer different questions
An invoice says "you owe me this amount by this date". A contract says what was agreed: scope, deadlines, revisions, ownership, and what happens if things go wrong. An invoice can prove a debt exists; only a contract proves what the debt was for.
When an invoice alone is fine
A one-off task under a few hundred dollars, for a repeat client you trust, with nothing to own afterwards (a quick edit, a one-hour call). Even then, an email thread confirming price and scope is worth keeping.
When you need a contract
- The project runs more than a week or two.
- You create something the client will own (design, code, copy, photos).
- There is a deposit, milestones or a retainer.
- The client is new to you.
For small jobs there is a middle ground: a one-page agreement. See do freelancers need a contract for small jobs.
Combine them: sign and pay in one step
The admin cost of "contract, then invoice" is why many freelancers skip the contract. Draft it now with Clinch: describe the job in a sentence, get a clean draft, send one link. Your client signs from their phone without an account, and the deposit is paid in the same step.