Extra Work Ordered on LINE, Customer Refuses to Pay: The Evidence Your Company Needs

The contract is half done. The customer's manager types in the LINE group, "Please add one more section, go ahead." Your site team does it because nobody wants to upset the customer. Nobody mentions the price. When the extra-work invoice arrives, the customer replies "I thought that was included in the original job" or "I had no authority to approve that", and may add that the extra work made delivery late.

This happens constantly in construction, installation, design and service work where the scope shifts along the way. This guide explains what the company should separate out, how to preserve the chat, how to check the authority of whoever gave the order, and how to record the effect on the delivery date. The closest related topics are in our guides on verbal contracts, electronic signatures in company contracts and the delegation of authority matrix.

The Short Answer

To collect for extra work, the company has to prove four things in sequence: the work was outside the original scope; the customer or its representative ordered it, or knew of it and accepted it; the person who ordered it had authority to bind the customer company (or the customer ratified afterwards); and the price, or the method of pricing, was agreed or at least the company can show a reasonable basis for the amount.

The law. A LINE message is not denied legal effect merely because it is electronic data, under Section 7 of the Electronic Transactions Act B.E. 2544. Section 8 treats electronic data that can be accessed and reused with its meaning intact as writing where the law requires writing. Section 9 sets the conditions for an electronic signature, and Section 11 lets a court admit electronic data as evidence and weigh it by the reliability of how it was created, stored and communicated. Whether the person who gave the order binds the customer is a matter of agency: Civil and Commercial Code Section 797, holding out under Section 821 and ratification under Section 823. Whether a job falls within the original scope is decided by reading the contract in good faith under Section 368, and delay and penalties are governed by Sections 379 to 383.

Our practical view. Extra-work disputes are usually lost on price and authority, not on the text of the message. The manager types "go ahead", nobody writes a price, and nobody writes how the delivery date moves. We recommend making it a company discipline that out-of-scope work always gets a message confirming scope, price and effect on delivery before it starts, even a short one that the customer accepts in the same chat.

The running hypothetical in this guide is a small rooftop solar installer in Nakhon Ratchasima. It took a job installing panels on a rice mill's roof for 860,000 baht, with delivery in 45 days. During the job the mill's plant manager ordered, in the LINE group, that the panels be extended to a second warehouse roof, with no mention of price. The company later worked out the extra work at 94,000 baht, and the extra work pushed delivery back 12 days. We call them "the Solar Company" and "the Mill".

1. Is This Work Inside or Outside the Original Scope?

Before thinking about evidence, answer whether the company can charge more at all. If the work is clearly inside the original scope, it cannot charge extra, even if the customer ordered it by chat. Compare it with the documents in this order:

1. The contract and annexes, the quotation, the drawings, the bill of quantities (BOQ) and the scope of work.
2. Conflicting quotations or purchase orders. If two documents disagree, see our guide on quotation and purchase order with conflicting terms.
3. Meeting minutes or earlier messages that record what was agreed.
4. Industry custom, which a court uses to interpret under Section 368, under which a contract is read in good faith with regard to ordinary usage.

In the example, the second warehouse roof is not in the original drawings or quotation, so it is clearly outside scope. The weakness is not scope, it is the missing price.

2. Does "Go Ahead" Bind the Customer?

Contracts generally need no particular form. A chat instruction can therefore be an offer, and starting the work where the customer can see it, together with the customer's conduct, can amount to acceptance, as explained in our guide on verbal contracts. The problems lie in the details:

• Scope of the instruction. "Please look at one more spot" is different from "go ahead". The first may be only an enquiry.
• Price. If price was never discussed, the customer may say it never agreed to pay more or assumed it was included in the original price.
• A clause in the main contract. Many contracts say amendments must be in writing and signed by an authorised person. The customer will raise this at once, although an amendment by conduct may still be provable in some cases.
• Acceptance of the work. If the customer has already used the extra work or paid part of it, that circumstantial evidence weighs more than the message itself.

Do not expect a court to read "go ahead" as agreement to a price that was only in the company's head, if the price never appears in the chat.

3. How Can a LINE Chat Be Used as Evidence?

Electronic messages can be used as evidence, but the weight depends on how they were kept. Under Section 11 of the Electronic Transactions Act B.E. 2544 a court looks at the reliability of how the data was created, stored or communicated, how its integrity was maintained, and how the originator was identified.

Our recommended practice:

• Keep both screenshots and the exported file. When an important instruction arrives, export that day's chat into the project folder and back it up in the company's storage, not on an employee's personal phone.
• Do not delete messages, and do not change phones without a backup. Missing messages or deleted stretches make a court doubt completeness.
• Note who is in the group. A LINE group that includes the manager, the customer's technicians and a purchasing officer shows who knew about the order. Record the members and the dates they joined or left, because someone who was in the group and did not object may help prove knowledge.
• Tie the account to a person. LINE display names can be changed. Keep evidence of whose account it is, such as a phone number matching a business card, or documents the customer sent from the same account.
• Signature. Section 9 concerns an electronic signature that identifies the signer and shows intent. An unsigned chat can still be evidence of intent, but that is different from signing a contract. See our guide on electronic signatures in company contracts.

If the dispute is large, have a lawyer plan how the electronic evidence will be put before the court from the start, for example who will testify to where the chat came from.

4. Who on the Customer Side Has Authority to Approve the Price?

Many companies find that the person giving orders on site is not the person who signed the contract, so the customer says the manager had no authority. Check three layers:

1. Actual authority (Section 797). An agent is someone the principal authorises to act for it. Look at powers of attorney, the position in the organisation chart, the company affidavit showing the authorised directors, and any clause in the main contract naming a project coordinator or representative.
2. Apparent agency (Section 821). If the customer company held a person out as its agent, for example by appointing that person project manager and letting them be the contact on all work, or by paying for extra work that person approved before, the customer company is liable to an outsider acting in good faith. The company doing the work must genuinely have believed the person had authority.
3. Ratification (Section 823). If the person giving the order had no actual authority but the customer company learned of it and accepted it, for example by using the extra work, paying part of it, or not objecting while knowing, that may count as ratification, which binds the customer company.

What the company should keep:

• The name, position and duties of the person who gave the order.
• Earlier occasions when the same person ordered extra work and the customer paid without dispute.
• Meeting minutes naming this person as coordinator or approver.
• Messages from the genuinely authorised person who saw the extra work and did not object.

There is a mirror image on your own side. If a site employee accepts extra instructions without going through anyone, the company may already be bound without knowing it. See the delegation of authority matrix to decide who may accept extra work and confirm prices on the company's behalf.

5. The Variation Order Process Before Starting Work

The most effective way to reduce disputes is not to start extra work until three things are confirmed: scope, price and the effect on delivery. A variation order does not need to be a long document; a short message the customer accepts is enough, unless the contract prescribes a form.

1. Receive the request. Record who asked, when and for what.
2. Assess. Check whether it is outside scope. Estimate price, materials, labour and the effect on delivery.
3. Send the confirmation message. Send it to the authorised person, not only to the site contact. State that without acceptance the company will not start the extra work.
4. Wait for acceptance. Ask for a reply of "approved" or a signed variation order, and keep evidence that it came from the authorised person.
5. Start work. Keep before and after photographs, plus time and material records.
6. Reflect it in the invoice. Issue an invoice that references the variation order number.

Sample message asking for confirmation of extra work (sample, adapt to the actual job)

Dear ____ (the Mill's authorised approver),
Following Mr/Ms ____'s instruction in the LINE group on ____ to extend the work to a second warehouse roof,
which is outside the scope of contract no. ____, we propose variation order VO-01 as follows:
1) Scope: ____ (as per the attached drawing)
2) Price of the extra work: ____ baht (including/excluding VAT). Payment: ____
3) Effect on delivery: moved from ____ to ____ (an additional ____ days)
4) We will start the extra work once we receive your acceptance.
Please reply "Approved VO-01" with your name and position.

If the customer pushes you to start first because it is urgent, send a short message such as, "We have received the instruction to carry out the extra work described. Price and delivery date will be confirmed within ____ days. Please reply to confirm we should start", and then fix the price as quickly as you can.

6. Recording the Effect on the Delivery Date So the Company Is Not Penalised

Extra work takes time, yet the main contract may still count from the original delivery date. If this is not recorded, the customer may later deduct the full penalty, which is a separate problem from price. See our guide on a customer deducting penalty or damages from payment.

A penalty under Sections 379 to 383 is an amount the debtor must pay when it does not perform as agreed. Section 383 lets a court reduce a disproportionately high penalty, but reduction is in the court's discretion and should not be the main plan. The key point is that delay caused by the customer, such as ordering extra work, sending information late, or not giving access to the site, is a defence for which the company should hold evidence that the delay is not its fault. If the customer refuses a performance tendered on time, it may also be a creditor in default under Section 207.

What to record when extra work arises:

Also write into the main contract that extra work, and delay caused by the customer, extends the delivery date by the agreed amount. Consult a lawyer before using wording that affects penalties.

7. If the Customer Now Refuses to Pay

The honest position. If the customer ordered the extra work and the company actually performed it but no price was agreed, the company can often still seek reasonable remuneration, for example on unjust enrichment under Section 406, or on the remuneration rules for work accepted by the customer under Sections 587 and 602. But the amount becomes a dispute. The customer will say it is too high, that it was already in the original job, or that it gained no benefit. The result depends on the facts and the court's discretion, so we cannot promise an outcome in advance.

The order we recommend:

1. Collect evidence. Exported chats, the original quotation, drawings, before and after photographs, time and material records, and evidence that the customer has used the work.
2. Separate the amounts. Invoice the extra work separately from the main work. The source of the figure must be explainable, for example unit prices from the original quotation or a comparable market price.
3. Claim the undisputed part first. If the customer also owes for the main work, claim that first. Do not merge the two issues, which would give the customer an excuse not to pay anything. See our guide on unpaid invoices from business customers.
4. Negotiate. Offer a way out, such as a small reduction in exchange for written acceptance of the work, or payment in instalments. Put any settlement in writing.
5. Send a demand letter. State the extra-work items, the date of the instruction, who gave it, the amount claimed and the payment deadline. Our demand letter service can help draft it tightly.
6. Prepare for a counter-allegation. If the customer replies that the company breached the contract or delivered late, see our guide on preparing a response to a breach of contract allegation letter, and do not stop the main work without checking the contract, because the company could be accused of breaching it.

If the customer rejects the extra work because it never signed an acceptance, see our guide on a customer not signing acceptance so you cannot invoice.

8. Checklist: Extra Work and Evidence

Before starting the extra work

• Checked that the work is outside the scope of the contract, quotation and drawings
• Have a message or variation order stating scope, price and effect on delivery
• The person who accepted is authorised, or there is evidence of delegation
• Recorded the name, position and phone number of the person who ordered it and the person who approved it

During the work and while keeping evidence

• Exported the chat for the day of the instruction and kept both screenshots and the export
• Noted the LINE group members and the dates they joined or left
• Took before and after photographs and recorded time, materials and labour for the extra work
• Kept evidence that the customer knew of or used the extra work

Delivery date

• Recorded the original date, the new date and the reason for the shift
• Obtained a message from the customer acknowledging the new date
• Kept evidence of delay caused by the customer

If the customer refuses to pay

• Invoiced the extra work separately and can explain the source of the amount
• Claimed the undisputed amount first
• Sent a demand letter that references all the documents
• Checked the contract before stopping work or withholding delivery

Further Reading

• Are verbal contracts enforceable in Thailand? — the rule on agreements made without documents
• Electronic signatures in company contracts — the difference between a chat and signing a contract
• Delegation of authority matrix — deciding who confirms prices for the company
• Unpaid invoices from business customers — the steps when a customer does not pay on time
• Preparing a response to a breach of contract allegation letter — when the customer says delivery was late
• Quotation and purchase order with conflicting terms — when two documents set the scope differently
• Customer deducts penalty or damages from payment — when the customer withholds money citing delay

Extra work with no price, no approver and no record of the delivery date is something the customer can dispute on every point. Confirm those three things before starting, every time.

We help review contracts and scope of work, prepare variation order templates, check chat evidence and the authority of the person who gave the order, and draft demand letters for extra work. For an initial consultation, call +66 92 254 2045 or send us the details. See also the demand letter service and contracts and business documents.

This guide is published by Suwanvara Law Firm — a Khon Kaen law firm established in 1986. General information only, not legal advice on a specific matter.