The four formulas I used, and when each one stopped a refund request
I wrote 150 delay emails between November and February—peak season for Royal Mail and An Post backlogs. I'm a sole trader handling customer service for three Shopify stores and two eBay accounts, all selling into the UK and Ireland. I needed templates that worked fast, sounded human, and kept refund requests under 8% of delayed parcels.
I tested twelve prompt formulas in Claude Sonnet 4.5 and Gemini Pro. Four of them handled 94% of the situations I faced. The other eight either sounded like a chatbot wrote them or triggered more angry replies than the original complaint. Here's what worked, with the exact prompts and the reasoning for when to use each one.
Formula one: initial delay (parcel is late but still moving)
When to use it: The tracking shows "delayed in transit" or "processing at depot" but the parcel hasn't been declared lost. Customer tone is neutral to mildly annoyed. You need to acknowledge the problem, give a realistic timeline, and offer one small gesture without opening the refund door yet.
The prompt:
Write a customer service email responding to a parcel delay complaint. Details: [paste customer's message]. Parcel tracking: [current status]. Tone: warm, accountable, no corporate jargon. Acknowledge the delay without over-apologising. Give a realistic delivery estimate based on current Royal Mail/An Post processing times (add 3–5 working days to the original estimate). Offer a £5/€5 discount code for the next order, expiring in 30 days. Do not offer a refund yet. End with a single line inviting them to contact you again if it doesn't arrive by [date]. 120 words maximum.
Why this works: The "3–5 working days" instruction stops the AI from promising next-day delivery when Royal Mail is running a week behind. The discount code is small enough that it doesn't cost you much, but specific enough that the customer feels heard. The expiry date nudges them back to your store. I used this formula 68 times. Eleven customers replied to say thanks. Three came back when the parcel still hadn't moved after five days, and I escalated to formula two.
What doesn't work: Asking the AI to "reassure" the customer or "build trust." Both phrases produce sentences like "We value your patience during this time," which sound like a script. The customer already knows you value their patience. They want a date.
Formula two: parcel declared lost or missing for 10+ days
When to use it: Tracking hasn't updated in ten days, or Royal Mail/An Post has confirmed the parcel is lost. Customer tone is frustrated or explicitly asking for a refund. You're legally obliged to refund or reship under the Consumer Rights Act 2015 (UK) and the European Communities (Unfair Terms in Consumer Contracts) Regulations 1995 (Ireland), so the email needs to offer both options clearly and move fast.
The prompt:
Write a customer service email responding to a lost parcel claim. Details: [paste customer's message]. Parcel has been missing for [number] days with no tracking updates. Tone: direct, apologetic, solution-focused. Acknowledge that the parcel is lost. Offer two options: (1) full refund processed within 2 working days, or (2) free reship sent today via tracked service. Ask them to reply with their choice. Include one sentence explaining that you're filing a claim with Royal Mail/An Post and this isn't their fault. No discount codes. 100 words maximum.
Why this works: Offering both refund and reship in the same email cuts reply time in half. Thirty-one of the 42 customers who got this formula picked reship, which saved me the Shopify transaction fee on a refund and kept the sale. The line about filing a claim with Royal Mail does two things: it shows you're taking the loss seriously, and it subtly reminds them that the courier failed, not you. I've had two customers reply to say "I didn't realise it wasn't your fault"—both picked reship.
What doesn't work: Asking the AI to "express empathy" or "apologise sincerely." You get three paragraphs of sorry. The customer doesn't want sorry; they want their money or their item. One sentence of acknowledgment is enough.
Formula three: customs hold (parcel stuck at Coventry or Dublin)
When to use it: Tracking shows "held by customs" or "awaiting clearance," usually on parcels coming from outside the UK/Ireland or going to Northern Ireland post-Brexit. Customer tone ranges from confused to angry, often because they've been asked to pay VAT or duty they didn't expect. You need to explain what's happening without sounding like you're lecturing them, and clarify who pays what.
The prompt:
Write a customer service email explaining a customs delay. Details: [paste customer's message]. Parcel is held at [location] for customs clearance. Tone: patient, educational, not defensive. Explain in two sentences what a customs hold means and why it happens. Clarify that [Royal Mail/An Post] will contact them directly about any charges—you cannot pay these on their behalf. Estimate clearance will take 3–7 working days based on current processing times. Offer to help if they have questions about the charges, but do not offer a refund unless the delay exceeds 15 working days. 130 words maximum.
Why this works: The "educational, not defensive" instruction stops the AI from writing "Unfortunately, customs delays are beyond our control," which reads as washing your hands of it. I used this 23 times. Four customers replied with questions about VAT thresholds, which I answered in one follow-up. Two parcels were stuck for 18 days; I sent formula two at that point and reshipped. The rest cleared within a week.
Trade-off: This formula works for customers who are genuinely confused. If the customer is already furious and blaming you for not declaring the VAT correctly, the AI will still produce a patient explainer, but it won't defuse the anger. I've had three of those. I wrote those replies myself.
Formula four: failed delivery (customer wasn't home, parcel at depot)
When to use it: Tracking shows "failed delivery attempt" or "card left." Customer either didn't see the card, doesn't want to collect from the depot, or is asking you to rearrange delivery. Tone is usually impatient. You need to give clear next steps without taking responsibility for something Royal Mail/An Post controls.
The prompt:
Write a customer service email responding to a failed delivery. Details: [paste customer's message]. Tracking shows a delivery attempt was made on [date] and parcel is now at [depot name]. Tone: helpful, practical, no blame. Explain their two options: (1) collect from the depot using the card left (include depot address and opening hours if available), or (2) rebook delivery via the Royal Mail/An Post website (include the tracking number). Add one sentence saying you cannot rebook on their behalf because the parcel is now in the courier's system. Offer to reship if the parcel is returned to you as undeliverable, but note that will add 5–7 days. 110 words maximum.
Why this works: The "no blame" instruction is critical. If the AI writes "We attempted delivery but no one was available," it sounds like you're blaming the customer for not being home. I used this 17 times. Fourteen customers collected from the depot. Two asked me to reship when the parcel was returned; I did, no charge. One accused me of lying about the delivery attempt. I refunded.
What doesn't work: Asking the AI to "encourage" the customer to collect from the depot. That produces sentences like "We encourage you to visit the depot at your earliest convenience," which sounds passive-aggressive. Just give the address and the hours.
The routing decision I made after 150 emails
I keep all four prompts saved in a Kryotta workspace with a comparison arena tab open. When a delay email comes in, I read the customer's tone first, check the tracking status second, then pick the formula. If I'm unsure, I run the same prompt through Claude Sonnet 4.5 and Gemini Pro side by side and send whichever reply sounds less like a template. Sonnet is better at the customs explainer; Gemini is faster at the failed-delivery steps.
The refund rate on delayed parcels dropped from 14% in October to 7% in February. I don't think that's because the emails are magic. I think it's because they're fast, they're specific, and they don't sound like I copied them from a help centre. The customer can tell a human checked the tracking and picked the right reply.
One thing I won't use AI for: the reply when a customer is already escalating to their bank or posting on social media. Those I write myself. The four formulas handle routine delays. They don't handle fury.
Questions people ask
Can I use these prompts in Shopify's built-in email editor or do I need a separate AI tool?
Shopify doesn't have AI built into the email editor yet. I paste the customer's message and tracking status into Kryotta, run the prompt, then copy the reply back into Shopify. Takes about 40 seconds. You could use ChatGPT or Gemini directly, but I like having all four templates saved in one workspace where I can compare outputs before I send.
What if the customer replies again and the AI-generated email didn't solve the problem?
I read every reply. If the first email didn't work—parcel still missing, customer still angry—I escalate to the next formula or write it myself. The templates handle the first response. They're not a loop you can run unsupervised.
Do these prompts work for couriers other than Royal Mail and An Post?
Yes, but you'll need to adjust the timelines. DPD and Evri move faster than Royal Mail, so the "3–5 working days" estimate in formula one would be too long. The structure stays the same; the details change.
Should I mention the AI wrote the email if a customer asks?
I don't volunteer it, but if someone asks directly I say I use AI to draft replies and I check every one before sending. No one has objected yet. The email either solves their problem or it doesn't—most customers don't care how you wrote it as long as it's accurate and fast.
If you're handling delay emails manually and it's eating two hours a day, these four prompts will get you most of the way there. I built my templates in Kryotta because I wanted to compare Claude and Gemini outputs side by side without switching tabs, but the prompts themselves will work in any AI tool that lets you set tone and word count. Start with formula one. You'll know within ten emails whether it's cutting your refund rate or just making you sound like a bot.
