Interim Valuation Calculator Nigeria: How to Prepare and Submit Progress Payments in 2026

For any Nigerian contractor working on a project with a contract sum above ₦10 million, the interim valuation is the most important document produced on the project — more important in practical financial terms than any drawing or specification. An interim valuation (also called an interim certificate, progress payment application, or stage payment claim) is the mechanism by which the contractor recovers money from the client for work already completed.

Get the valuation right, and cash flows into the project to pay workers, suppliers, and subcontractors. Get it wrong — incomplete sections, calculation errors, missing retention deduction, incorrect previous certificate amount — and payment is delayed, disputed, or reduced. On a large contract running for 12 to 24 months, the compound effect of poorly prepared interim valuations can put a contractor into serious financial difficulty even on a profitable project.

Our free Interim Valuation Calculator produces a properly formatted Nigerian interim valuation statement aligned to standard QS practice, ready for submission to the client's quantity surveyor or project manager.

What Is an Interim Valuation?

An interim valuation is a periodic assessment of the value of work executed by the contractor up to a given date. In Nigerian construction contracts, interim valuations are typically prepared:

• Monthly (most common on large projects)
• At agreed stage completions (slab, roof, finishing)
• On demand (rare — typically for small projects with milestone payments)

The valuation is typically prepared jointly by the contractor's quantity surveyor and the client's quantity surveyor (or checking QS), agreed, and then certified by the client's representative for payment. Payment is then made within the contractual payment period (typically 28 to 30 days after certification under NEC3, JCT, and Nigerian standard form contracts).

Components of a Nigerian Interim Valuation

1. Gross Value of Work Executed

The total value of all work completed to the valuation date, assessed against the contract BOQ rates. For each BOQ item, the percentage of completion is estimated and multiplied by the BOQ rate and quantity to give the gross value. Alternatively, on simpler projects, each bill section is assessed as a percentage complete and the section value calculated accordingly.

2. Value of Materials On Site

Under most Nigerian standard form contracts, properly protected, unfixed materials delivered to site can be included in the interim valuation at a percentage of their invoiced value (typically 75% to 90% to provide a margin against damage or theft). Materials in transit are generally not included. This provision recognises the cash flow burden on Nigerian contractors who must purchase and store materials weeks or months before they are incorporated into the works.

3. Retention Deduction

Retention is a percentage of the gross value held back by the client as security against defects and non-completion. Standard Nigerian contract retention rates:

• During construction: typically 5% of gross value
• At practical completion: retention reduces to 2.5% (half released)
• At end of defects liability period: remaining 2.5% released
• Maximum retention (total retained during construction): often capped at 5% of contract sum

4. Previous Certificates (Amount Already Certified)

The net amount certified on all previous interim certificates is deducted from the current gross value minus retention to give the amount due on the current certificate. This prevents double payment and ensures each certificate covers only the incremental value added since the last certificate.

5. Other Deductions (if applicable)

Depending on the contract, additional deductions may include: advance payment repayment (where a mobilisation advance was given), liquidated damages (for delay, though these should not be applied without written notice), and any contra charges agreed in writing.

The Standard Formula

Current Certificate Value =
  (Gross value of work done to date
   + Value of materials on site
   - Retention deducted to date)
  - Sum of all previous certificates
  - Any other agreed deductions

How to Use the Interim Valuation Calculator

1. Contract details: Contract name, contractor name, employer name, contract sum, contract start date, valuation date.
2. Bill section valuations: For each bill section, enter the total bill value and percentage complete to date.
3. Materials on site: Enter total delivered material value and the applicable percentage for inclusion.
4. Retention rate: Enter the contractual retention percentage (typically 5%).
5. Previous certificate total: Enter the sum of all amounts previously certified (cumulative).
6. Other deductions: Advance payment recovery, contra charges, etc.

The calculator outputs a formatted valuation statement showing gross value, materials on site, retention deduction, cumulative value, previous certificates, and net current certificate amount — ready to print and submit.

Tips for Nigerian Contractors Preparing Interim Valuations

• Submit on time: Most Nigerian contracts have a contractual submission deadline (e.g., the last working day of each month). Late submission delays the payment clock and gives the client's QS an excuse to push payment into the next month.
• Measure on site, not from the programme: Claim what you have actually done, measured on site, not what the programme says should have been done. Overclaiming leads to disputes and clawback on subsequent certificates.
• Keep a running gross total: Your cumulative gross value should match the client's QS calculation within ±5% at each valuation. Large discrepancies indicate measurement disagreement that should be resolved before the certificate is issued.
• Maintain a site materials register: If you are claiming materials on site, maintain a delivery register with invoice numbers, quantities, and storage location. The client's QS will verify on-site quantities during the joint valuation inspection.

Frequently Asked Questions

What is the difference between an interim certificate and an interim valuation in Nigeria?

The interim valuation is the calculation prepared (usually jointly) that determines the amount due. The interim certificate is the formal document issued by the client's representative (architect, engineer, or QS) authorising payment of the certified amount. Both refer to the same periodic payment event but represent different documents in the payment chain.

Can a Nigerian client withhold an interim certificate?

Under most standard form contracts, the client's representative is contractually bound to certify each interim valuation within a fixed period (typically 14 to 28 days). Refusal to certify without valid contractual grounds is a breach of contract. Contractors should document all valuation submissions with date-stamped records and consider formal dispute resolution if certification is unreasonably withheld.