Tender Addendum

Section 1

Purpose

A Tender Addendum is a formal document issued during the tender period to correct errors, omissions or ambiguities in the tender documents, or to incorporate design changes that arise after tenders have been issued. It forms part of the tender documents and, if the tenderer is awarded the contract, becomes a contract document. Every addendum must be numbered sequentially, issued to all tenderers simultaneously, and formally acknowledged by each tenderer before the tender return deadline.

Addenda should be avoided wherever possible — they are evidence that the tender documents were not fully prepared before issue, and they impose additional pricing burden on tenderers during an already constrained tender period. Where an addendum is unavoidable, the QS must assess whether the additional pricing work requires a tender period extension, and issue the extension to all tenderers simultaneously.

RICS Tendering Strategies (2015) confirms that all changes to tender information during the tender period must be captured in a formal addendum and issued to all tenderers simultaneously. Informal changes — verbal instructions, email confirmations not issued to all tenderers, revised drawings issued to one tenderer only — are a serious breach of tender integrity and, for public sector projects, may constitute a breach of procurement regulations.

Section 2

Key Principles

RICS Tendering Strategies (1st edition, 2015), Section 3.9: any change to the tender documents during the tender period must be captured in a numbered addendum issued to all tenderers simultaneously.
RICS E-Tendering (2nd edition, 2010): addenda must be uploaded to the e-tendering portal and tenderer acknowledgement of receipt must be recorded electronically.
JCT Tendering Practice Note (2012): if an addendum materially changes the scope, specification or contract conditions, tenderers should be given reasonable additional time to re-price.
Public Contracts Regulations 2015 / Procurement Act 2023, Regulation 56: supplementary information (including addenda) must be made available to all economic operators simultaneously; failure to do so may render the procurement process unlawful.
NRM 2 (2nd edition, 2021): where an addendum revises BQ quantities or adds new measured items, the revision must follow NRM 2 measurement rules and description conventions.

Section 3

Practical Application

Step 1

Identify the need for an addendum: from a tender query that reveals a genuine error/omission; from a design change instructed by the client; from a change in statutory requirements (e.g. a planning condition added after tender issue); or from an error in the contract conditions or contract particulars.

Step 2

Obtain client approval before issuing an addendum that arises from a client-instructed design change. Document the instruction in writing. For error corrections, the QS may issue the addendum on their own authority but should notify the client.

Step 3

Prepare the addendum document: give it a sequential number (Addendum No. 1, No. 2, etc.); state the original tender document reference(s) being amended; clearly describe the change using 'delete' and 'insert' language; attach revised drawings or specifications where applicable; include revised BQ items measured to NRM 2 rules where quantities change.

Step 4

Assess whether the addendum requires a tender period extension. If the addendum requires tenderers to re-measure items, re-price a significant element, or review contract conditions, a reasonable extension (typically three to five working days for minor addenda; one to two weeks for substantial changes) must be granted.

Step 5

Issue the addendum to all tenderers simultaneously via the e-tendering portal. Request a formal acknowledgement of receipt from each tenderer. Set a deadline for acknowledgement — tenderers who do not acknowledge should be chased by the QS.

Step 6

Update the tender document index: record the addendum number, issue date, description, and the tender period extension granted (if any). This forms part of the tender audit file.

Step 7

If the addendum substantially changes the scope or makes the tender documents materially different from those originally issued, consider whether the tender should be withdrawn and re-issued as a new exercise — particularly for public sector procurements where the addendum may affect the project's advertised scope.

Step 8

After tender returns are received, verify that each tenderer has priced the addendum items. Non-compliance with a numbered addendum is a tender irregularity and must be addressed in the tender analysis and clarification round.

Section 4

Common Mistakes to Avoid

Issuing revised drawings or specification changes directly to tenderers without a formal addendum — informal changes are not captured in the contract documents and create scope disputes post-contract.
Not assessing the need for a tender period extension when issuing a substantive addendum — tenderers rushed by a late, significant addendum may submit inflated contingency allowances or request extensions unilaterally.
Failing to obtain acknowledgement of receipt from all tenderers — an unacknowledged addendum may not have been incorporated into a tenderer's price, causing post-tender clarification complications.
Issuing multiple addenda for the same section — numerous addenda create confusion about which version is current. Where multiple changes affect the same section, consolidate into a single addendum where possible.
Not checking addendum compliance during tender analysis — tenderers who have not priced addendum items have submitted a non-compliant tender; this must be identified and resolved, not overlooked.

Section 5

APC Competency & Quick Reference

APC Competencies: Procurement & Tendering (L2) | Legal & Regulatory Compliance (L1) | Cost Management (L1) | Commercial Management (L1)

What must a formal Tender Addendum contain?

A Tender Addendum must contain: (1) sequential addendum number; (2) original tender document reference(s) being amended; (3) clear description of each change (delete/insert language); (4) revised drawings or specifications where applicable; (5) revised BQ items (NRM 2) where quantities change; (6) statement of any tender period extension granted; and (7) acknowledgement slip for tenderers to return.

When does a tender addendum require a tender period extension?

An extension is required when the addendum materially changes the scope tenderers must price — e.g. revised BQ sections requiring re-measurement, changes to contract conditions, addition of a significant work package, or revised programme requirements. Minor clarifications (confirming existing information) do not require an extension. Extensions must be issued to all tenderers simultaneously.

Can a tender addendum be used to change the contract form or conditions?

Yes, but with caution. Amending contract conditions via an addendum is permissible but creates complexity — all tenderers must clearly understand and accept the revised conditions. For public sector projects above threshold, changes to contract conditions post-OJEU/FTS notice may require re-advertisement if the change is material enough to attract different tenderers. Legal advice should be sought for substantive condition changes.

Section 6

Tender Addendum Checklist

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Need for addendum identified and reason documented (error / design change / statutory change)

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Client approval obtained (for client-instructed design changes)

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Addendum document prepared: sequential number, document references, delete/insert language, revised drawings/BQ items

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Tender period extension assessed and confirmed (granted where substantive re-pricing required)

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Addendum issued to all tenderers simultaneously via e-tendering portal

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Formal acknowledgement of receipt requested from all tenderers

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Non-acknowledging tenderers chased before tender return deadline

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Tender document index updated (addendum number, date, description, extension granted)

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Addendum compliance verified in each tender return during tender analysis

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Full addendum record retained as part of tender audit file

Section 7

CPD Learning Outcomes

Prepare a formal Tender Addendum to correct errors, omissions or design changes during the tender period, ensuring it is correctly formatted, numbered and issued simultaneously to all tenderers.
Assess whether a tender period extension is required following an addendum, and apply the correct procedure for granting and documenting extensions in compliance with RICS Tendering Strategies (2015).
Explain the consequences of issuing informal tender changes without a formal addendum, including the risk of post-contract scope disputes and, for public sector clients, the risk of procurement challenge.

Section 8