Good Seal
Notes

4 September 2026 · 1 min read

Addendum or amendment: what's the difference

Both change a contract after it has been signed. They are not interchangeable, and using the wrong one can create a document that contradicts itself.

A contract needs to change after both sides have already signed it. The instinct is to reach for whichever word sounds more familiar - usually "amendment" - and attach a page. The two words describe different kinds of change, and using the wrong one can leave the contract contradicting itself.

Amendment: changes the original terms

An amendment alters something the contract already says - a payment amount, a deadline, a clause that turned out to be unworkable. It replaces or edits existing language, and the original wording is understood to no longer apply where the amendment overrides it.

Addendum: adds something new

An addendum attaches terms the original contract never covered at all, without touching anything that is already there. A lease that adds a pet policy six months in is an addendum, not an amendment - the original terms about rent and duration are untouched, and the addendum simply sits alongside them.

Why mixing them up is a real problem

Label new terms an "amendment" when they do not reference or replace anything in the original, and it becomes genuinely unclear whether the old terms still apply alongside them. Label a real change an "addendum," and a court may read the original clause as still standing next to a document that contradicts it - because nothing said the original was being replaced.

  • Changing something the contract already says: amendment.
  • Adding something it never mentioned: addendum.
  • Either way, reference the original contract by name and date, and have both parties sign again.

Good Seal treats a change to a contract the same as any other document - its own sealed PDF, its own audit trail. There is no separate "amendment mode": send it as its own signed document that names the contract it changes.

Good Seal is a free DocuSign alternative: upload a PDF, place the fields, email a link. The other side signs in the browser and everyone gets a sealed copy.

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