A client accepts your quote. Then something changes: they want another room painted, an extra landing page designed, a different integration built, a faster deadline, or a new approval step added. You do not always need to throw away the original quote and start again. In many cases, a short quote addendum is cleaner.

A quote addendum is a written update that sits beside the original quote. It explains what changed, what the change costs, how the timeline is affected, and what the client is approving. It keeps the original quote intact while giving both sides a clear record of the new agreement.

What is a quote addendum?

A quote addendum is a short document that modifies an already-sent or already-accepted quote. It does not replace the original quote unless you clearly say it does. Instead, it references the original quote and documents a specific change.

Use it when the original quote is mostly still correct, but one part needs updating. That might be scope, price, timeline, assumptions, materials, delivery method, payment schedule, or approval wording.

When to use an addendum instead of a revised quote

Use a quote addendum when the change is specific and the original quote remains useful. For example, a web studio might add one extra landing page to a site build. A contractor might swap a material allowance after a client chooses a different finish. A consultant might add a workshop to a strategy package.

Use a revised quote when the change is large enough that the whole pricing structure, scope, or presentation needs to be rebuilt. If you are changing most line items, moving to a different package, or replacing the original project direction, a revised quote is easier for the client to understand.

Use a formal change order when the work is already underway and the extra work affects contract scope, job cost, or schedule. The practical difference is often small, but the language matters. If you need more detail on pricing extra work after approval, this guide to change order wording for quotes is a useful companion.

What every quote addendum should include

A good addendum is short, but it should not be vague. Include these fields every time:

  • Original quote reference: quote number, client name, project name, and original quote date.
  • Addendum number: for example, Addendum 01 or Addendum A.
  • Reason for the change: one plain-language sentence explaining what prompted the update.
  • Scope change: what is being added, removed, swapped, accelerated, or clarified.
  • Price impact: additional fee, credit, revised total, or confirmation that there is no price change.
  • Timeline impact: extra days, revised milestone date, or confirmation that the schedule is unchanged.
  • Assumptions and exclusions: what the price depends on and what is still not included.
  • Payment impact: whether a deposit, milestone payment, or final balance changes.
  • Approval wording: the line the client signs or accepts before work begins.

External project-management guidance is consistent on one key point: scope changes should be documented in writing. NetSuite’s overview of change orders explains why the change process should be addressed before work changes hands, and Procore notes that change order requests and communications should be handled in writing.

Copy-ready quote addendum template

Use this as a simple starting point and adapt it to your business, location, and contract requirements.

Quote Addendum [number]
Original quote: [quote number and date]
Client: [client name]
Project: [project or job name]

Reason for addendum
This addendum updates the original quote to reflect [brief reason for change]. All terms of the original quote remain unchanged unless specifically updated below.

Updated scope
The following work is now included: [describe added or changed work].

Price impact
This addendum adds [amount] to the original quote. The revised total is [amount], excluding/including applicable taxes as stated in the original quote.

Timeline impact
This change will [add X business days / move the delivery date to X / not affect the current timeline].

Assumptions and exclusions
This price assumes [assumptions]. This addendum does not include [exclusions]. Any further changes will require written approval before work begins.

Payment impact
[Payment due on approval / added to next milestone / added to final balance / requires deposit of X before scheduling].

Approval
By approving this addendum, the client authorizes the updated scope, price, timeline, and payment terms described above.

Approved by: [name, date, signature or written approval]

Example addendum wording for common situations

Agency example: extra landing page

Scope update: Add one additional campaign landing page using the approved design system. Includes layout, copy placement, responsive build, and one revision round.

Price impact: Adds $850 to the original quote. Revised project total: $6,250.

Timeline impact: Adds three business days to the build timeline once page content is supplied by the client.

Contractor example: material upgrade

Scope update: Replace the originally quoted standard tile allowance with the client-selected premium tile at the updated supplier cost.

Price impact: Adds $1,240, including material cost difference and additional installation time.

Assumption: Price is based on supplier availability as of the addendum date. Delivery delays may affect the installation schedule.

Consultant example: added workshop

Scope update: Add one 90-minute stakeholder workshop for up to eight participants, including preparation, facilitation, and summary notes.

Price impact: Adds $1,100 to the current engagement.

Payment impact: Due with the next scheduled milestone invoice.

How to name and track addenda

Addenda get messy when they are treated like casual email threads. Use a simple naming system so the client, your team, and your accounting records all point to the same version.

  • Quote Q-1042
  • Quote Q-1042 Addendum 01
  • Quote Q-1042 Addendum 02

If you already use version labels, make sure the addendum number does not fight with the quote version number. For example, Quote v2.0 can still have Addendum 01 if that addendum is the first approved change after v2.0. For a deeper system, read this guide to quote version control.

Pre-send checklist

Before you send the addendum, check that it answers the client’s real questions:

  • Can the client see exactly what changed?
  • Is the original quote clearly referenced?
  • Is the additional price shown as a clear amount, not just a vague note?
  • Does the addendum say whether taxes are included or extra?
  • Does the timeline impact use specific dates or business days?
  • Are assumptions and exclusions easy to understand?
  • Is there a clear approval line?
  • Have you kept a copy with the original quote?

How ququ helps with quote addenda

In ququ, the practical goal is to avoid rebuilding work you have already priced. You can keep reusable products and templates for common change types, create a clean branded PDF, and protect internal costs that do not need to be shown line by line to the client. If a scope change affects margin, hidden internal costs and automatic redistribution help keep the client-facing quote tidy while still keeping your numbers realistic.

The best addendum is not long. It is clear, specific, and approved before the extra work starts. That is what protects your time, your margin, and the client relationship.