Addendum

In plain English: an addendum is a one‑page change note attached to an existing agreement. It adds or replaces a small part of the deal — a new deliverable, a revised deadline, a price change — without redrafting the whole contract. Both sides sign it so the update is part of the same deal.

TL;DR: use an addendum when the shape of the relationship stays the same but a detail moves. It is different from rewriting the whole paper. It is also different from starting a fresh statement of work: an addendum edits what you already agreed; a statement of work describes a new job under the same standing terms.

Freelancers and agencies use addenda for everyday changes: extending a timeline, swapping one asset for another, adding a round of revisions, or increasing a fee after a scope change. In many industries the same idea is called a change order or a variation. The job is the same: write the change down, price it, and have both sides agree before the extra work starts.

Addendum versus amendment: the words are often used as synonyms. In practice, people call a short, self‑contained update an addendum (“Addendum No. 2 to the Services Agreement”) and a general rewrite an amendment (“The parties amend clause 5 (Payment) as follows”). Either can work as long as the text is clear about what is changing and what stays the same.

A clear addendum names five things: (1) the original contract it attaches to (title and date), (2) exactly which section or schedule it changes, (3) the new words or the added scope, (4) what the updated price and dates are, and (5) that all other terms remain as before. If a statement of work exists, the addendum should say whether it edits that SOW or the master services agreement above it.

For scope moves, many teams prefer a small change order template: “Add one extra landing page, delivered by 14 November, fee +£600, invoiced on approval.” That is an addendum by another name. The benefit is speed and a tidy paper trail. When the last invoice is raised, those notes explain why the number moved.

When to use an addendum instead of a new SOW: if you are still on the same project and you are not changing the standing legal terms (ownership, liability, governing law), an addendum or change order is usually enough. If it is a new project with its own deliverables and timeline, a new SOW keeps each job separate and avoids rolling changes across unrelated work.

What to avoid: do not slip big legal changes into a casual addendum. If you are changing who owns the work, moving IP assignment from “on payment” to “on delivery”, or changing the liability cap or indemnity, that belongs in a clearly labelled amendment to the main contract, not in a one‑line scope tweak. It is also easy to forget to say whether added items are within the existing revision limit or have their own.

Signing and records: an addendum should be signed by both parties, just like the original. Day to day this is an e‑signature on one frozen version. Keep the addendum with the original agreement and any SOWs so the file shows the final wording. If the contract has an “entire agreement” and “variations” clause, follow what it says about how changes are made (usually “in writing and signed by both parties”).

On Contracts.io, both sides edit, agree and sign on one shared link (“two‑sided contracts”). For a small change you do not need a new file: add the change on the page, agree it, and sign once. The client does not need an account and never pays. That keeps one version and one audit trail.