Assumptions, and the day work stops being yours
An assumption is a conditional price, and writing it as anything less wastes the clause. The useful form names the condition and its consequence in the same breath: text arrives in final form and further rewrites are re-estimated; one named individual gives approval and additional approvers extend the review; the existing system behaves as its documentation claims and investigating any divergence is chargeable; third-party access is available from the first day and idle time caused by its absence counts against the estimate. Each line is a sentence the client agreed to while feeling optimistic, which is why raising money against it later feels administrative rather than confrontational. Freelancers who have no assumptions section end up asking for more money on the strength of how hard they have been working, which is not an argument anybody has ever won. The second clause decides when the work stops belonging to you. Acceptance should be an event with a date, not a feeling the client eventually arrives at. Define it as a written list of defects, measured against the criteria in the agreement, delivered inside a stated review window; say that silence through that window counts as acceptance; and say what separates a defect from a change, since that distinction is where the whole dispute lives. A defect is the thing you promised behaving otherwise. A change is a thing you never promised. Attach the final payment to acceptance rather than to satisfaction, because satisfaction has no date and can be withheld indefinitely by anybody with a busy quarter and an unpaid invoice.
The rest of the document should be short and boring. Deliverables named in nouns the client would recognise. Their obligations carrying dates exactly as yours do, so a late supply of material moves the deadline automatically instead of becoming a negotiation. A change procedure that says who may request one, in what form, that pricing happens before work, and that unaffected parts of the job continue meanwhile. A payment schedule tied to events rather than to moods. And the exclusions, which are the clause people skip because everything in it feels too obvious to write down, right up until the week somebody assumes hosting, migration, copywriting, photography, training or a year of support was included all along. Length is not the point and a page can do the job. What matters is that a stranger reading it could tell, without asking either of you, whether the work is finished.
Say which document wins
Your carefully written agreement can be silently overridden by whatever arrives afterwards: a purchase order with terms on the back, a supplier portal whose tick box binds you to a procurement policy you never read, an email chain agreeing something different. Add a precedence line stating that this document governs scope, price and timing, and read what the portal asks you to accept before accepting it. A solicitor, not a glossary entry, gives legal advice, and a contract worth arguing over is worth an hour of one's time; the useful point is simply that somebody drafted the terms you are working under, and if it was not you then they were not written with you in mind.