How to write an invoice

The work is finished, but the office cannot tell what the customer approved or where the extra cable came from. If you wait until then to decide how to write an invoice, the bill gets disputed.

The blunt answer to how to write an invoice is this: start with the accepted quote and approved scope changes, not memory. Identify the job, bill only authorised work, apply the correct local tax treatment, state the balance and send the issued copy to the billing contact.

Before you write the invoice, lock down what can be billed

An invoice is the final issued document for the job. Build it from the records created before and during the work.

Confirm the billing trigger

Read the customer agreement. Find the event that allows you to invoice. It might be completion, a milestone, delivery of materials or another agreed event.

Do not invoice a milestone because the calendar says it is time. Check that the milestone happened and that the required sign-off, photos or completion record exists.

For a completed job, get the site contact to confirm completion before the crew leaves. If accounts payable needs a separate completion certificate or reference, collect it now.

Pull the accepted documents

Open the accepted quote, work order, purchase order and site record. Do not work from the draft quote sitting at the top of an email chain.

The quote tells you what was sold. The work order tells you what the crew was authorised to do. The site record tells you what happened. The purchase order tells you which reference the customer's accounts team expects.

Match every extra to written approval

Find the signed or recorded approval for each scope change. Match the description and amount to the work performed.

The ceiling is lined. The quote excluded chasing. The customer approves extra cable and chasing before work continues. That approval supports an extra invoice line.

Without approval, the invoice does not create approval after the fact. Separate the billing problem from the document. Speak to the customer, decide what can be billed and record the outcome before issuing the invoice.

In the United States, the approved record is commonly a change order. Use the practical steps in how to write a change order before extra work starts to control the next extra.

Confirm who receives the bill

Ask for the legal customer name, billing address, accounts-payable contact and email address. The person who approved the work may not be the person who processes the invoice.

Ask whether the customer needs a purchase-order number, property code, asset number or job reference. Put that reference in its own field. A correct total can still sit unpaid when accounts cannot match it to an order.

Read the payment terms

Use the payment terms the customer accepted. Do not replace them with whatever wording happens to be on an old template.

Confirm the payment method and the reference the customer must use. If the agreement covers deposits, progress claims, retention or credits, carry that treatment into the invoice without changing the deal.

Know which job document you are looking at

Each document has one job. Mixing them creates duplicated charges and arguments about scope.

Estimate

An estimate gives a likely amount or range based on what is known. It is not the final payment request.

If unknown conditions remain, inspect them before moving from estimate to quote where possible. Record any assumptions and exclusions.

Quote

A quote states the offered scope and price. Once accepted, its scope and price become the basis of the invoice.

If the scope is still being sold, stop and deal with that first. The guide to writing a quote shows how to describe the work, exclusions and acceptance before the crew starts.

Work order

A work order gives the crew authorised job instructions. It should identify the site, task, access notes and job references the field team needs.

It is not automatically a customer invoice. Use it to prove what the crew was sent to do and to collect the completion details needed by the office.

Approved scope change

This record changes the accepted work. It should state what changed, what it adds or removes, the agreed amount or billing method and the customer's approval.

Call it a variation in the United Kingdom and Australia. Call it a change order in the United States and Canada. Keep the market's term on customer-facing documents.

Invoice

An invoice requests payment for goods or services supplied. It identifies the amount due and how the customer can pay it.

An invoice is not a replacement contract. It should follow the agreement rather than introduce new scope or payment terms.

Receipt or payment record

A receipt or payment record confirms that money arrived. An unpaid invoice does not prove payment.

When payment arrives, record the date, amount and payment reference against the invoice. Keep the original invoice value visible even when its balance becomes zero.

Invoice fields to collect

Collect these fields before building the invoice. Some may be required by local tax or licensing rules. Others help the customer match the bill to the job. The country sections below tell you where to check what is legally required.

Your working list should include:

• Your business's legal name, trading name where used, address and contact details.
• The customer's correct name, billing address and contact details.
• A unique invoice number.
• The issue date and the date or period when the work was supplied.
• The site address when it differs from the billing address.
• A clear description of the supplied work or goods.
• Quantities and units where the billing agreement uses them.
• The subtotal, visible credits or discounts, tax treatment and final balance.
• The agreed due date or payment terms.
• Payment instructions and a payment reference.
• Quote, work order, purchase-order and approved scope-change references where needed.

A logo and brand colour can help the customer recognise the document. They do not replace the business, transaction or tax information required by the responsible body.

Trade or contractor licence details may also be required on business documents in some places. Ask the licensing body responsible for your trade and location which details belong on an invoice. Write its answer into your locked template fields.

United States

Check whether the business must register for, collect and display sales tax with the state department of revenue or tax agency responsible for the transaction. The IRS directory of state government websites (opens in a new tab) helps you find the correct state body; the state body sets the sales-tax rules.

For federal tax identity questions, including EIN information, use the IRS EIN guidance (opens in a new tab). Do not send state sales-tax questions to the IRS.

Ask your state contractor licensing board whether a contractor license number must appear. For an electrical, plumbing or mechanical trade license, ask the state or city licensing office responsible for that trade. Keep license, labor and change order terminology within US customer documents.

United Kingdom

Check ordinary invoice information with HMRC's invoice guidance through GOV.UK (opens in a new tab). If the business is VAT registered or the transaction raises a VAT question, check the HMRC VAT invoice requirements (opens in a new tab).

Do not invent a VAT treatment from the customer's status or from an older invoice. Confirm how the transaction must be recorded, then apply that treatment consistently to the lines and totals.

Ask the body responsible for your trade whether licence or registration details belong on the document. For gas work, ask the Gas Safe Register about registration questions. Call an approved scope change a variation on UK documents.

Canada

Check GST/HST registration, collection, invoice support and record questions with the Canada Revenue Agency (opens in a new tab). Use the treatment that applies to your business and transaction rather than copying an invoice from another province or territory.

Ask the provincial or territorial trade licensing and safety authority whether trade licence details must appear. Ask the municipality about its business licence requirements, not federal tax treatment.

Use change order for an approved scope change. Keep the approval record with the invoice so the customer can match the extra to the agreed work.

Australia

Check GST registration and tax-invoice requirements with the Australian Taxation Office (opens in a new tab). Do not add GST, remove it or label a document as a tax invoice without checking the treatment that applies to the business and sale.

Ask your state or territory licensing regulator whether a trade or contractor licence number and other details must appear. The responsible regulator depends on the work and location.

Use variation for an approved change. Keep its reference beside the added invoice line so the customer can trace the amount back to approval.

How to write an invoice from the job record

Once the billing trigger and local requirements are settled, turn the job record into one issued invoice.

Give it a unique invoice number

Assign one number that has not been used by the office or field team. Do not let two staff members create separate invoices for the same job.

Keep the numbering method stable. The customer, bookkeeper and payment record should all point to the same reference.

Add the dates

Record the issue date. Add the service date or service period so the customer can identify when the work happened.

State the due date or agreed terms without contradicting the accepted quote or contract. Do not add a fresh deadline because it suits the current cash position.

Identify both parties and the site

Use your correct legal business details. Add the customer's correct billing identity, not just the site contact's name.

Show the service address when it differs from the billing address. For work across several assets, units or properties, identify which location each important line belongs to.

Add matching references

Reference the accepted quote, work order and purchase order where the customer uses them. Reference each approved scope change beside the extra it supports.

Keep internal job codes, but do not make the customer decode them. Pair each code with plain words describing the site and work.

Write line items that survive an accounts-payable check

A useful line tells the reader what was supplied and where. “Labour and materials” is often too vague to match against a quote or site record.

Name the task, location and result

Start with the thing worked on. Add the room, asset or area. State the completed task.

For example, name the bathroom exhaust fan, the roof ducting and the four downlights. Do not replace those nouns with “electrical works completed”.

Split lines where the agreement needs them

Use separate lines when the customer approved separate tasks, stages or extras. Keep a scope change separate from the original quoted work.

Do not split every screw and cable tie merely to make the invoice look detailed. The line structure should help the customer match the invoice to the accepted documents.

Handle fixed-price work correctly

For a fixed-price job, invoice from the accepted quoted amount. Do not rebuild the customer price from actual labour hours and supplier receipts after completion.

Your internal labour cost, material cost, overhead allowance and markup belong in job costing. They are not required as customer-facing lines unless the billing agreement calls for that detail.

Handle time-and-material work correctly

Use the recorded quantities, agreed units and agreed prices. Timesheets, material issues and site records must support the amounts.

Do not reconstruct missing labour from memory at the end of the month. Find the missing timesheet or site record before issuing the invoice.

Show labour and materials only when useful

Separate labour and materials when the agreement, tax treatment or customer process requires it, or when the split helps explain an agreed charge. Keep a fixed-price task together when that is how it was sold.

An invoice should explain the bill. It does not need to expose your internal cost build-up or profit.

Build the totals without hiding the arithmetic

Put each adjustment where the customer can see how the final balance was reached.

Start with the line-item subtotal. Add an agreed discount or credit as a separate adjustment rather than quietly changing a line price.

If the customer paid a deposit or earlier progress amount, show the original value and the amount already paid. Then state the remaining balance. Do not erase the original charge.

Apply sales tax, VAT, GST/HST or GST only after checking the correct treatment with the authority named in the country section. Label the tax clearly. Do not invent a rate or registration detail.

Check the arithmetic twice. Add the lines independently, check the adjustments and compare the final balance with the job documents.

Worked example: invoice INV-1847 for the Oak Street bathroom

This is the house electrical example. Every figure is a sample currency unit, not a rate card.

R. Chen at 14 Oak Street received estimate E-1847 with a range of 900–1,400. The accepted quote was Q-1847 for 1,105. It covered a 150mm bathroom exhaust fan ducted through the roof and four LED downlights.

The ceiling was lined, and the quote excluded chasing. Extra cable and chasing were approved on site as a 160 scope change. That makes invoice INV-1847 total 1,265.

The invoice can show the document chain like this:

Use “change order” for the approved 160 in the United States and Canada. Use “variation” in the United Kingdom and Australia. The approval reference should sit beside that line in the real document.

No tax, deposit, due date, payment method or approval document number is given in the sample. Do not invent those fields. Fill them from the actual agreement and local tax checks on a real job.

Copy-ready blank invoice template

Copy the fields into a document, spreadsheet, accounting system or paper form. Lock the permanent business and tax fields. Leave the job fields editable.

INVOICE

Business legal name: [Business name]
Trading name: [Trading name, if used]
Business address: [Address]
Contact details: [Phone and email]
Tax registration details: [Only the details required for this business and transaction]
Trade or contractor licence details: [If required by the responsible licensing body]

Invoice number: [Unique reference]
Issue date: [Date]
Service date or period: [Date or period]
Due date or payment terms: [Agreed terms]

Bill to: [Legal customer name]
Billing address: [Address]
Billing contact: [Name and email]
Service address: [Job site]
Customer reference or purchase order: [Reference]
Quote reference: [Accepted quote]
Work order reference: [Work order]

DESCRIPTION | QUANTITY/UNIT | AMOUNT
[Authorised task, location and result] | [If useful] | [Amount]
[Approved extra and approval reference] | [If useful] | [Amount]

Subtotal: [Amount]
Discount or credit: [Amount and reason]
Tax: [Correct label and amount]
Invoice total: [Amount]
Earlier payments or deposit: [Amount]
Balance due: [Amount]

Payment method: [Method]
Payment details: [Payment details]
Payment reference: [Invoice number or required reference]
Notes: [Short customer-required information]

Save one clean master. Do not reuse an issued customer invoice as the next template; old names, purchase-order numbers and bank details travel with it.

Add payment instructions the customer can use

State the accepted payment method and the reference the customer should include. Put bank or online payment details in a saved field rather than typing them afresh each time.

When payment details change, confirm the change through a separate contact channel. Do not rely on an email reply inside a thread that could have been intercepted.

Keep late-payment wording tied to the signed terms and local rules. Do not add a fee or interest charge that the customer did not accept or that you have not checked for the location.

A short invoice email is enough:

Subject: Invoice [invoice number] — [job reference] — [site]

Hello [billing contact],

Attached is invoice [invoice number] for the completed work at [site].
The balance due is [amount] under the agreed payment terms.
Please use [payment reference] with payment.

Please reply if your accounts team needs another job record.

Regards,
[Name]

Issue and store the invoice without losing control

You can make an invoice in a template, spreadsheet, accounting system or paper book. The tool matters less than unique numbering, correct fields and a preserved issued copy.

Separate permanent fields from job fields. Lock the legal business name, remittance details and confirmed tax information. Edit the customer, site, references, dates, lines and balance for each job.

Compare the draft with the accepted quote, approved changes and local tax requirements before sending it.

Export or save the issued version so later edits do not overwrite it. Record when it was sent, who received it and which email address or delivery method was used.

A handwritten invoice can work when it is legible, uniquely numbered and contains the required information. Give the customer a copy and copy the issued document into the office record. Do not leave the only record in a vehicle or paper pad.

Follow the invoice through payment

Send the invoice to the person who can process it. Attach any completion record or approved scope-change document the customer requires, but do not bury the amount due under unnecessary site paperwork.

If payment does not arrive, confirm that accounts received the invoice before calling it a dispute. Check the email address, purchase-order reference and required backup.

Send reminders against the agreed due date. Keep the message factual: invoice number, issue date, balance and payment instructions. Record each contact against the job.

Post part payments against the same invoice. Leave the original invoice total visible and reduce the outstanding balance. When the final payment arrives, record its date, amount and reference, then mark the balance paid.

With Yes Foreman, the crew can record completion notes and approvals from the field before the office prepares the invoice.

Correct an issued invoice without breaking the record

Fix a draft freely before it is issued. Once the customer has received an invoice, do not silently replace the file under the same reference.

Preserve the original. Use the credit, cancellation, amendment or replacement method required by your accounting process and local tax rules. Make the link between the old and new records clear.

Explain the correction in plain words. Send it to the same billing contact and state which amount or detail changed.

A corrected invoice is not a place to add unapproved work. Resolve the scope and approval first. Then create the required supporting record and invoice treatment.

Close the job with job costing, not invoice guesswork

The invoice tells the customer what to pay. Job costing tells you whether the original sold work made money.

On Oak Street, the original quote was 1,105. Known job cost was 850. Measured against that original quote, profit was 255 because 1,105 − 850 = 255.

Margin was about 23% because 255 ÷ 1,105 ≈ 23%. Markup was 30% because 255 ÷ 850 = 30%.

How to write an invoice and how to measure profit are separate jobs. Do not calculate profit from the 1,265 invoice. The cost of the 160 approved scope change is not given, so combining 1,265 with the known 850 job cost would invent profit.

Use the profit margin calculator with your own complete job figures. Feed missed labour, wasted materials and weak scope controls into the next quote, not into an unexplained customer charge.