10 Common Tendering Mistakes Quantity Surveyors Make (And How to Avoid Them)
Tendering is where projects are won and lost. These are the mistakes that cost quantity surveyors — and their clients — the most money.
Every quantity surveyor has a tendering war story. The prelims section priced for the wrong programme duration. The subcontractor quote included that quietly excluded half the scope. The PC sum carried to the summary at the wrong figure. Individually, each mistake is embarrassing. Collectively, they can turn a profitable project into a loss-making one before a spade has hit the ground.
This guide covers the ten most common tendering mistakes — and what to do about each one.
1. Not Reading the Preambles
The preambles are the specification clauses that define exactly what is included in each bill rate. They are also the section of the tender documents most commonly skimmed or ignored entirely.
This is a costly mistake. Preambles routinely include obligations that significantly affect the cost of work — specific material standards, fixing methods, surface preparation requirements, testing obligations and making good. A rate priced without reading the relevant preamble clause is a rate priced in the dark.
The fix: Before pricing any section of the bill, read the relevant preamble clauses in full. Mark up anything that affects your pricing assumptions. If a preamble clause is ambiguous or contradicts the drawings, raise a tender query — don't assume.
2. Missing the Tender Addenda
Most tenders of any complexity will include addenda — clarifications, corrections and additional information issued during the tender period. Missing an addendum can mean pricing superseded information, including quantities that have been corrected or specification items that have been changed.
The fix: Keep a numbered log of every addendum received. Check the log against the employer's list at tender return. If you are using a tender portal, check it daily during the tender period — addenda are not always accompanied by email notifications.
3. Pricing Provisional Sums as Zero
Provisional sums — both defined and undefined — represent work that cannot be fully detailed at tender stage. Some tenderers price them at zero on the basis that they are provisional and will be instructed separately. This is wrong and potentially contractually dangerous.
Under JCT, provisional sums must be carried in the tender at the stated sum. Under NEC4, provisional sums function differently but still require a considered approach. Pricing a defined provisional sum at zero when the contract requires it to be included can create a discrepancy in the contract sum that causes problems throughout the project.
The fix: Price every provisional sum at the figure stated in the bills. If you believe the figure is inadequate, note it in your tender qualifications — do not simply omit it.
4. Including Subcontractor Quotes Without Checking the Scope
This is one of the most expensive mistakes in tendering. A subcontractor quote arrives, looks competitive, and gets included in the tender. The contract is won. Then the subcontractor raises their order and it becomes apparent their quote excluded half the scope — groundworks, builder's work, attendance, making good, or any number of items that were in the bill but not in their price.
The fix: Before including any subcontractor quote, check it against the relevant bill section line by line. Identify every item in the bill that falls within the subcontractor's scope. Confirm in writing that their quote covers all of these items. If it does not, either get a revised quote or price the gaps yourself.
5. Underpricing Preliminaries
Preliminaries are the section of the tender that most commonly goes wrong. Site establishment, management, supervision, temporary works, welfare, health and safety — these costs are real and significant, yet they are frequently underpriced, particularly when tendering under competitive pressure.
Common prelims pricing mistakes include:
- Pricing site management for fewer weeks than the programme requires
- Forgetting to include the cost of the CDM principal contractor obligations
- Underestimating scaffold requirements
- Missing traffic management and access costs
- Forgetting the cost of temporary utilities — power, water, telecoms
The fix: Build your prelims from the ground up against the programme. Price each item individually — do not apply a percentage and hope for the best. Sense check the total prelims as a percentage of measured works against your benchmark for similar projects.
6. Ignoring the Programme
The programme is the commercial backbone of a tender. It drives the prelims, the resource allocation, the plant requirements and the cash flow. Yet many tenders are priced without a programme having been properly thought through.
Pricing a project against an unrealistic programme creates problems that compound throughout the contract. Prelims based on a 40-week programme become a loss the moment the project runs to its inevitable 52 weeks.
The fix: Prepare a realistic programme before pricing prelims. The programme should reflect the actual sequence and duration of operations, not a back-calculated target. If the employer's required completion date cannot be achieved without significant acceleration, price the acceleration — or flag the issue in your tender.
7. Failing to Identify and Price Risk
Every project has risks. Ground conditions, weather, interface with other contractors, design development, supply chain reliability — these are foreseeable uncertainties that experienced contractors price into their tenders. Ignoring them does not make them go away. It just means you absorb them when they materialise.
The fix: Prepare a risk register for every tender of significant value. For each identified risk, assess the probability and the potential cost impact. Include a risk allowance in your tender — either within rates, within preliminaries, or as a separate contingency line. Be transparent with your commercial team about what risks have been priced and what has been excluded.
8. Arithmetic Errors in the Summary
This sounds too basic to include in a list of professional mistakes. It isn't. Arithmetic errors in tender summaries are more common than the profession likes to admit — and the consequences can be severe. A misplaced decimal, a missed carry-forward, or a wrongly referenced cell in a spreadsheet can add or subtract hundreds of thousands from a tender sum.
The fix: Never self-check your own arithmetic. Have a colleague — ideally a senior QS — independently check every summary page before submission. Check the carry-forward from every section to the summary. Check the summary total against your internal estimate. If the two figures are significantly different, find out why before submitting.
9. Submitting Without Qualifications
Most tenders contain assumptions. Assumptions about ground conditions, programme, access, working hours, the scope of nominated subcontract packages, the extent of attendance obligations. When those assumptions are wrong — as they sometimes are — the contractor who submitted without qualifications has no protection.
Qualifications are not a sign of weakness. They are a sign of commercial competence. A well-drafted qualification can protect the contractor's position on a significant risk item while remaining competitive on price.
The fix: List your assumptions and qualifications clearly in the tender letter. Be specific — a vague qualification offers little protection. Have your qualifications reviewed by a senior QS or commercial manager before submission. Be aware that some employers require tenders to be submitted without qualifications — if this is the case, price the risk instead.
10. Missing the Submission Deadline
This is the mistake that renders every other mistake irrelevant. A late tender is typically a disqualified tender. Most public sector procurement portals close automatically at the deadline. Most private sector employers enforce their deadlines strictly.
Late submissions happen for predictable reasons — last-minute subcontractor quotes, a final review that runs over time, a portal upload that takes longer than expected. They are almost always avoidable.
The fix: Set your internal submission deadline at least two hours before the actual deadline. Allow time for portal uploads, printing, binding and delivery if required. Diarise the deadline on day one of the tender period. Never assume a client will grant an extension — assume they will not.
The Common Thread
Looking across these ten mistakes, the common thread is preparation. The tenders that go wrong are almost always the ones where the preparation was rushed — where the documents were not read carefully, the programme was not thought through, the subcontractor quotes were not checked, and the summary was not independently reviewed.
Tendering under competitive pressure is demanding. The temptation to cut corners is real. But the cost of a tendering mistake — in lost margin, in claims, in damaged relationships — almost always exceeds the time saved by cutting the corner in the first place.
A Final Checklist
Before submitting any tender, ask yourself:
- Have I read every preamble clause relevant to my pricing?
- Have I received and incorporated all addenda?
- Have I priced every provisional sum at the stated figure?
- Have I checked every subcontractor quote against the bill scope?
- Have I priced prelims against a realistic programme?
- Have I identified and priced the key project risks?
- Has someone else independently checked my summary arithmetic?
- Have I listed my qualifications and assumptions clearly?
- Am I submitting at least two hours before the deadline?
If you can answer yes to all nine questions, you have done everything within your control to submit a competitive, complete and commercially sound tender.
Go Further with QS Support
QS Support members get access to the Complete Tender Pricing Checklist — a comprehensive section-by-section checklist covering every stage of the tender process from pre-tender review through to post-submission actions.
Members also get access to live regional cost benchmarks, NEC4 and JCT contract guides, and monthly CPD webinars relevant to the profession.
