The Thumbs-Up Isn't a Signature: Making Chat Approvals Defensible

A few months back, a client sent a thumbs-up on WhatsApp at twenty past nine in the evening. It was attached to a message about an extra £6,800 of joinery. Everyone relaxed. The work started on the Monday. Six weeks later, the same client asked why the final account was higher than the figure they remembered agreeing. The thumbs-up was there, of course. But so was a long thread about a different door finish, two voice notes, and a deleted message that nobody could quite recall.

That is the quiet problem with chat-based approvals. They are immediate, human and reassuring. They are also thin evidence when money and deadlines are in dispute. UK project teams are running more decisions through WhatsApp, Teams and text than most contract administrators would be comfortable with. The answer is not to ban the tools. It is to make the approval survive the trip from phone to file.

Why the thumbs-up happens

Chat approvals happen because they work in the moment. A site lead needs an answer before the merchant closes. A client is on a train and cannot open a PDF. A subcontractor sends a photo of a missing part and asks whether to proceed. Typing 'yes' takes two seconds. Drafting a variation instruction takes two days and a meeting.

I understand the appeal. The risk is not that people are being dishonest. It is that the message rarely captures the things a decision actually needs: who had authority, what exactly was included, what it cost, and what it excluded. A thumbs-up is a mood. A decision needs a boundary.

What 'approved' actually needs to prove

If a chat approval is ever tested, four questions tend to come up.

1. Who approved it, and were they entitled to?
2. What exactly was approved, including scope and exclusions?
3. How much was it, and on what payment terms?
4. When did the approval take effect, and what happened next?

A screenshot of a green tick rarely answers all four. Sometimes it answers none. That is why the evidence rule should be simple: a chat message can start the decision, but it should not be the only record of it.

The four-part capture rule

When someone approves something by message, capture four things before work or money moves.

The sender and the authority. Save the contact name alongside the message. If the approval comes from someone new, check they can commit the client or the business. 'Can you confirm you're approving this on behalf of X?' is a fair question, not an insult.

The scope in plain words. Reply with a short summary: 'So that's the additional joinery to plots 4 and 7, excluding ironmongery, as per the quote dated 3 November.' Ask for a yes to that summary, not to the original vague message.

The number and the timing. Put the price, the payment terms and the start date in the same message. If the figure is an estimate, say so. If it is fixed, say that too.

The next step. Name what happens next: 'I'll issue a confirmation email and an instruction sheet today. Work starts Monday unless you tell me otherwise.' This turns a chat into a process.

The 24-hour email confirmation

A short email within a day of the chat is the cheapest insurance in project delivery. It does not need to be formal. It needs to be clear.

Subject: Confirmation of approval — additional joinery, plots 4 and 7

Hi [name],

Following our WhatsApp exchange this evening, I'm confirming the position as I understand it:

• Scope: additional joinery to plots 4 and 7, excluding ironmongery
• Cost: £6,800 plus VAT, fixed
• Programme: start Monday 24 November, completion within five working days
• Payment: invoice on completion, 14-day terms

You approved this by message at 21:20 today. If anything above is wrong, please reply by 5pm tomorrow. Otherwise we'll proceed on this basis.

That last line matters. It gives the other side a clear window to correct the record. If they reply 'yes, that's right', you have a decent trail. If they go quiet, you have a reasonable basis to proceed and a dated record of what you understood. If they disagree, you have found the problem before the work started rather than after.

When to stop and insist on a proper signature

Some things should not be approved by chat at all. I would put the following in that category:

• Changes to contract terms, payment terms or retention
• Anything that alters the critical path or a contractual completion date
• Approvals above a threshold your business sets in advance — £5,000 is a common line, but pick your own and stick to it
• Decisions that cross a financial year or a funding approval gate
• Anything a lender, insurer or auditor is likely to inspect

In those cases, the chat can be the heads-up. The signature is the decision. Say so kindly and early: 'Happy to get this moving — I just need the formal instruction signed before we release the order.' Most clients accept that. The ones who push back are usually the ones you want the paper trail for.

A quick test before you start work

Before you act on any chat approval, ask yourself one question: if the person who sent this message left the business tomorrow, could a stranger understand what was agreed and why?

If the answer is no, you are not being cautious by waiting. You are being sensible. A thumbs-up is a nice way to keep things moving. It is a poor way to finish an argument.

Keep the chat. Save the screenshot. But put the decision somewhere it can be read without context. That is the difference between a message and a record.