I Asked 9 AI Assistants to Write a Late Payment Follow-Up Email. Here’s What I Got.
The first three questions in this series were opinions. Which tool should I use? Should I tell customers? Where do I start? Good questions, but any AI can give you a view.
This time I gave them a job.
The question: “Write me a follow-up email to a client who hasn’t paid their invoice in 30 days.”
Every Australian small business owner has been here. The invoice is out. Thirty days have passed. Nothing. You need to chase it without burning the relationship. It’s a real task with real stakes, and it’s exactly what AI is supposed to be good at.
Same prompt. All nine apps. No follow-up questions answered. Here’s what happened.
One thing worth noting before we get into it: almost every AI offered to go further. “Want a firmer version?” “I can tailor this with your details.” “Let me know if you need alternatives.” I didn’t take any of them up on it. That’s the point. Most people won’t. They’ll take the first response, do a quick edit, and send. So that’s what we’re judging, the cold first draft, not the polished version after three rounds of back-and-forth.
New to the series? Meet the panel first →
Manus 🥇
Every other AI wrote me an email. Manus built a website.
Three versions, polite, firm, urgent, hosted at a live URL with a proper invoice follow-up template interface. Manus didn’t just answer the question; it shipped a small product.
The emails themselves are solid. Version 1 is a gentle nudge. Version 2 names the 30-day overdue status and mentions late fees. Version 3 goes full business mode, ALL CAPS subject line, explicit consequences, 24-hour response window. Most small business owners will live between versions 1 and 2, but having all three laid out makes the escalation path obvious.
If you want more than an email and have a few minutes to explore, this is the most complete response in the set. The website is actually live, you can browse the templates here.
Copilot 🥈
One email. The friendliest of the lot. Copilot picked up my name from context and pre-filled the signature as “Frank”, a small touch that shows it’s paying attention.
The tone sits closer to a text message than a business email: “consider this a friendly nudge in case it slipped through the cracks.” For a good client you know well, that might be exactly right. For someone you’ve never met or a client with a history of late payments, it’s probably too soft.
It offered firmer alternatives on request, but didn’t volunteer them. You have to know to ask.
Gemini 🥉
Two emails plus a pro-tips section, a format several AIs used this round. Option 1 is friendly (“I know how busy things can get”). Option 2 flips to a PAST DUE subject line and asks for explicit confirmation of receipt.
The tips are worth reading: re-attach the invoice so they don’t have an excuse to delay, and check your bank records before you hit send. That second one is practical in a way that feels like hard-won advice rather than template filler.
Meta AI
The only AI to offer a “short + no-fluff” version, four lines, asks for a payment date, done. For a lot of business owners, that’s the one they’ll actually use. The polite and firm versions are competent, and the tip about only mentioning late fees if they’re actually in your contract is worth heeding. Threatening fees you can’t enforce backfires.
One thing to watch: the formatting had a glitch. The dollar sign and amount got separated mid-sentence, and a raw [X] placeholder leaked through in the late fee clause. Fine if you read it carefully before sending, but a reminder that AI-generated templates need a human pass before they go out.
ChatGPT
One email, no options, no tips. “Kind regards.” If you want something professional and forgettable that won’t offend anyone, this is it.
ChatGPT is confident enough in its default that it doesn’t offer alternatives unless you ask, and it does mention that 45- or 60-day versions are available if you need them. The email itself is clean and would pass muster in any industry. Just don’t expect it to reflect your voice or your relationship with the client.
Claude
Two emails. Fewest words of any response in this set. No preamble, no pro-tips, one line of context for each option.
The gentle version covers the “it probably slipped through” scenario well. The direct version has the best single line of the whole exercise: “Could you let me know the status of payment, or an expected date I can plan around?” That phrase asks for commitment without pressure, and it frames the request around your needs rather than their failure.
Perplexity
One email, formal, “Kind regards.” If you closed your eyes and swapped the logos, you’d struggle to tell this apart from the ChatGPT response. Both are competent, both are forgettable, both offer to escalate if you ask.
Perplexity’s strength in previous rounds was knowing when to pull in external sources. A task test like this doesn’t play to that. It just writes a decent email and gets out of the way.
DeepSeek
One email, clean, and it opens a door most others don’t: “If there’s a reason for the delay, or if you need to discuss a different payment arrangement, please let me know.” For Australian small businesses dealing with clients who are genuinely struggling, that line matters.
DeepSeek also uses a different placeholder format, [INVOICE_NUMBER] in caps instead of [Invoice Number] in title case. Small thing, but it gives the template a slightly different feel. More like a business system than a personal note.
Grok
Warmest tone of the nine. “We truly value our partnership and the work we’ve done together”, Grok is betting hard on the relationship angle. It also has the most complete signature block (including company website) and formats the payment details as a bullet list, which makes it easier for the client to act.
If you’re chasing a client you genuinely want to keep, this is a strong starting point. If you’re three invoices deep with a slow payer, the warmth might land as weakness.
The Verdict
Most useful overall: Manus, for giving you an escalation framework rather than a single email. If you only ever chase one invoice, any of these will do. If you chase invoices regularly, having the three-tier system ready is worth more than any individual email.
Best single line: Claude, “an expected date I can plan around” is doing real work in a small number of words.
Most surprising: Copilot pre-filling “Frank” as the sender. Nobody else did that. If your AI assistant knows who you are, it should show up in the output.
Most off-base: Perplexity. Not bad, just the wrong tool for the job. Its search-backed strengths don’t show up in a writing task.
Watch before you send: Meta AI’s template had formatting errors. Proof-read anything AI-generated before it goes to a client. Always.
What This Tells Australian Small Business Owners
The AI that writes the best follow-up email isn’t necessarily the right AI for your business. The question is what you actually need:
- Relationship-first? Copilot or Grok.
- Escalation path ready? Manus.
- Just get it done, no fuss? ChatGPT or Perplexity.
- Something with an edge? Claude’s direct version.
- Client might be struggling? DeepSeek’s payment arrangement line.
The real test isn’t which AI wrote the best email in isolation. It’s which AI wrote the email you’d actually send, in your voice, to your client, in that specific moment. None of them nail that without some editing. But several of them get you 80% of the way there in about ten seconds, which is the point.
Series scorecard
Track how all 9 assistants perform across every question, with links to every actual response.
This is post 4 in the series. Follow the series →
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Sources
Manus response: https://manus.im/share/4NMHjadADvXie7wPZ3wuBe
Copilot response: https://copilot.microsoft.com/shares/Qjvdx5g6CRPwy5BXGePZz
Gemini response: https://g.co/gemini/share/2cf95fb00353
Meta AI response: https://meta.ai/share/sSh66ULrsG
ChatGPT response: https://chatgpt.com/s/t_6a229cf30fec8191ab2024f0ec73bc7e
Claude response: https://claude.ai/share/b40017f1-8149-4688-87e2-d35b83459678
Perplexity response: https://www.perplexity.ai/search/53216163-bbc0-4119-89c5-6ef95dc29857#0
DeepSeek response: https://chat.deepseek.com/share/dryys0vikd3xi6t71b
Grok response: https://grok.com/share/bGVnYWN5LWNvcHk_6397ec05-2c2b-4d2b-b49d-28eb16ce0392
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