Quotation vs Invoice vs Proforma Invoice: What's the Difference? (Nigeria Guide)

Quick answer: A quotation is a price estimate sent before any commitment — the client has not yet agreed to anything. A proforma invoice is a more formal preliminary bill, often used for customs, imports, or when a client needs a document that looks like an invoice to secure internal approval or funding, but it is not yet a final demand for payment. An invoice is the final bill, issued once goods are delivered or services rendered, that formally requests payment.

Side-by-Side Comparison

Quotation: The Starting Point

A quotation is your opening offer — a client asks "how much will this cost?" and you respond with a detailed price estimate. At this stage, nothing has been agreed, no work has started, and the client is often comparing your quotation against others before deciding. See our full guide on how to write a construction quotation in Nigeria for the exact fields to include.

Proforma Invoice: The Middle Ground

A proforma invoice sits between a quotation and a final invoice. It looks like an invoice — with an itemised breakdown, totals, and your business details — but it is explicitly not a demand for payment yet. It is most commonly used in Nigeria for:

• Import and customs purposes — a proforma invoice is required by shipping companies, customs agents, and sometimes the Central Bank of Nigeria (CBN) as part of Form M documentation when importing goods or equipment
• Client-side budget approval — a corporate client's finance or procurement department may require a proforma invoice to internally approve and release funds before you can issue the "real" invoice and begin work
• Formalising a quotation — some businesses issue a proforma invoice instead of a quotation once a deal is close to confirmed, as it looks more official to a client's finance team

A proforma invoice typically includes everything a final invoice does — description, quantities, prices, totals — but is clearly labelled "PROFORMA INVOICE — NOT A DEMAND FOR PAYMENT" or similar, and usually has no invoice number in the sequential series used for real, payable invoices.

Invoice: The Formal Demand

The invoice is the final, binding bill — issued once you have delivered the goods or completed the agreed work (or milestone). Unlike the quotation or proforma, an invoice represents an actual obligation to pay, typically within a stated due date. See our guide on how to write an invoice in Nigeria for the full breakdown of required fields.

How the Three Documents Flow Together

1. Client requests a price → you issue a quotation
2. Client is close to confirming, or needs it for internal approval / import documentation → you issue a proforma invoice (optional step, not always required)
3. Client formally accepts, work begins or goods are delivered → you issue the invoice, requesting actual payment
4. Client pays → you issue a receipt confirming payment received

Not every transaction needs all four documents — small, informal jobs often skip the proforma invoice entirely and go straight from an accepted quotation to a final invoice. Larger corporate transactions and any import-related purchase are far more likely to require the proforma step.

Why Getting This Right Matters

Using the wrong document at the wrong stage creates real friction. Sending an "invoice" when you mean a quotation can make a client think you are demanding payment for work you haven't started or agreed. Conversely, a corporate client's finance department may reject your final invoice if it doesn't match the proforma invoice they used to secure internal budget approval. Keeping the three documents distinct — and consistent with each other in pricing and scope — avoids these payment delays entirely.

Proforma Invoices in Import and Customs Documentation

For Nigerian businesses that import equipment, machinery, or specialised building materials, the proforma invoice plays a specific regulatory role. Before an import can be processed, the buyer typically needs a proforma invoice from the foreign supplier to open a Form M through their bank — a mandatory documentation step for importing goods into Nigeria. This proforma invoice states the agreed price, quantity, and terms of the shipment and is used by the bank and customs authorities to verify the transaction before the goods arrive and the final, binding invoice is issued. If you supply imported materials or equipment as part of a construction project, understanding this distinction helps you explain to clients why a proforma stage may be necessary before you can confirm final pricing and delivery timelines.

How Corporate Procurement Processes Use All Three Documents

Larger Nigerian companies and government agencies typically have a formal procurement process that relies on this document sequence quite strictly: a quotation (or several, from competing suppliers) to select a vendor, a proforma invoice or local purchase order (LPO) to formally authorise the purchase internally, and a final invoice submitted only once goods are delivered or services completed, matched against the LPO before payment is released. If you regularly work with corporate or government clients, understanding and following this sequence — rather than trying to shortcut straight to a final invoice — often speeds up payment rather than slowing it down, because you are working within the client's existing approval workflow instead of against it.

Keeping the Three Documents Consistent

Whichever combination of documents a transaction requires, the golden rule is consistency: the scope, quantities, and pricing described in the quotation should match the proforma invoice (if one is issued), which should in turn match the final invoice. Discrepancies between these documents — even small ones caused by an updated material price or a client-requested change — should always be explicitly noted and, ideally, re-confirmed with the client in writing before the final invoice is sent. Silent discrepancies are one of the most common reasons corporate finance departments delay or query a payment.

Frequently Asked Questions

Do I always need to issue a proforma invoice?
No. It is only necessary for import/customs documentation or when a client's internal process specifically requires one before releasing budget. Most everyday transactions move directly from an accepted quotation to a final invoice.

Can the price on a proforma invoice change before the final invoice?
It shouldn't, in principle — but because a proforma invoice is not legally binding, minor adjustments (e.g. exchange rate movement on imported materials) are sometimes reflected in the final invoice, ideally with the client informed in advance.

Is a quotation the same as an estimate?
They are often used interchangeably, though some contractors treat an "estimate" as a rougher, non-binding figure and a "quotation" as a more precise, formal offer the client can accept outright.

What is a Local Purchase Order (LPO) and how does it relate to these documents?
An LPO is issued by the buyer (not the seller) to formally authorise a purchase, usually after reviewing a quotation. It functions similarly to an accepted quotation from the buyer's side and is commonly required before a supplier will proceed with a corporate or government order in Nigeria.