Question answered
What should I check before paying a builder's deposit or mobilisation payment?
The direct answer
Pay only when the purpose, entitlement, protection and next consequence are clear.
A request described as a deposit or mobilisation payment is not automatically unreasonable, but the label tells you very little. Before paying, establish what the payment buys, where the contractual entitlement sits, what evidence accompanies it, whether ownership or security changes, and what happens if the appointment or programme changes.
The percentage alone cannot answer whether the request is acceptable. A smaller unsupported payment can be risky, while a larger payment tied to identified materials, security and a controlled contract may be explainable. The decision must be tested against the actual proposal.
Decision ruleDo not release an early payment merely to preserve a date. First convert the request into a written schedule of purpose, deliverables, protection, ownership, timing and recovery.
Why this matters
The decision sits across several workstreams.
Early payments can move leverage and risk before equivalent work has been completed. The owner needs to understand what changes immediately after payment.
Different requests may fund design work, site setup, long-lead materials, contractor cash flow or a reservation in the programme. Those are different propositions and require different evidence.
The payment should fit the intended building contract and valuation process. An informal request made before the contract is settled can create ambiguity about what has been bought and which terms apply.
The readiness test
Five checks to put on the record.
Contractual basis
Identify the proposed contract, the clause or agreed term supporting the payment, and whether the contract is already executed.
Evidence to identify: Signed contract or clearly agreed pre-contract terms, payment schedule and invoice.Defined use
Break the amount down between design, preliminaries, site establishment, materials, subcontractors and other stated purposes.
Evidence to identify: Itemised mobilisation schedule, quotation, purchase order or subcontract evidence.Ownership and security
If the payment relates to materials or goods, establish where they are, how they are identified, when title passes and what protection exists if delivery or performance fails.
Evidence to identify: Vesting terms, identification records, insurance, bond or other project-specific protection where agreed.Programme consequence
Record what the contractor commits to do after receipt and the dates by which defined outputs or site activities should occur.
Evidence to identify: Accepted programme, procurement schedule and dated deliverables.Financial and insurance checks
Confirm the payee, bank details, tax treatment, insurance position and any independent commercial advice appropriate to the sum and project.
Evidence to identify: Verified account details, insurance certificates and advice from the contract administrator, quantity surveyor or solicitor where appointed.What to do now
A controlled sequence for the owner.
Name the payment
Ask the contractor to define whether it is an advance, deposit, reservation, materials payment or payment for completed pre-construction services.
Request the breakdown
Require a written allocation and the evidence supporting each part.
Align it with the contract
Confirm how the amount will appear in later valuations and what happens on delay, cancellation or termination.
Check protection
Decide whether ownership terms, insurance, a bond, staged release or another control is proportionate.
Record the decision
Keep the request, advice, agreed basis, payment evidence and post-payment obligations together.
Warning signs
Pause and ask for clarity if any of these appear.
- The only reason given is that the contractor always charges this amount.
- The payment is required urgently but the contract, scope or programme is still being negotiated.
- A materials payment does not identify the materials, location, ownership or insurance.
- The invoice description is materially less specific than the explanation given verbally.
- Nobody can explain how the payment will be treated in the first valuation or if the start is delayed.
From project experience
The practical pattern.
Urgency is often presented as a programme issue, but payment clarity and programme protection should be developed together. Paying quickly does not itself create a reliable start date.
This is a professional observation, not a statistical claim or a project-specific conclusion.Questions to put on the record
Ask for answers that can be checked.
- What exactly does this payment purchase or secure?
- Where is the entitlement recorded?
- Which deliverables and dates follow payment?
- If materials are included, where will they be held and when does ownership pass?
- How will the amount be shown in later valuations?
- What happens if the contract is not executed, the programme changes or the contractor cannot proceed?
Frequently asked questions
What owners usually ask next.
Is a 10% or 20% mobilisation payment normal?
There is no single percentage that establishes fairness or safety across different projects. Test the amount against its purpose, contract, supporting evidence, protection and the contractor's immediate obligations.
Should I pay for materials before delivery?
That can arise on long-lead items, but the owner should obtain project-specific advice on identification, title, insurance, storage, insolvency risk and the contract mechanism before paying.
Does an invoice provide enough protection?
An invoice records a request for payment. It may not settle scope, ownership, programme, repayment or contractual consequences.
Sources, editorial responsibility and boundaries
Published by: Planning & Project Advisory Ltd.
Editorial lead: Anthony Lilley. Planning, design coordination and owner-side project context.
Publication record: Published 26 August 2026. Professionally reviewed 3 September 2026. Geographic scope: England.
Method: Primary sources, professional observations and the use of drafting tools are explained in the editorial policy.
Limit: This material is general information. It is not legal advice, technical approval, a compliance certificate or authority to commence work.