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Something the customer already paid for is out of stock: substitute it, refund that amount, or wait

When you're out of stock on something already paid for, you'll know how to separate that item from the rest of the order and choose between a substitute, a partial refund, or a wait, depending on whether you know the restock date.

By Yodai · Published on September 6, 2026 · Updated on October 12, 2026

6 min read

This case isn't about a delay: the item is simply out of stock, and you don't have a date you can trust. You take an order for three items, $54 total. Two days later you discover one of them is out of stock, with no solid date for when more will come in. The customer already paid. Do you ship the other two and refund the third, swap it for something similar, or ask them to wait?

There's no single answer that always works. There's one question that decides which of the three fits: do you know when you'll have that item again, yes or no? If the answer is "yes, in three days" or "yes, the supplier's shipment comes in Thursday," you're already halfway there: you can offer to wait, with a specific date, short and firm, and let the customer decide if it's worth it to them. If you sell remotely, through your website, by phone, or by WhatsApp, the General Law for the Protection of Consumers and Users requires you to deliver without undue delay and, unless you agree otherwise, within 30 calendar days of the purchase at the latest (Article 109). If the answer is "I don't know" or "they don't make this model anymore," waiting stops being an honest option, and the same law is clear about it: when what you sold isn't available, you have to tell the customer, and they have to be able to get back what they paid without undue delay. If you delay that refund without justification, they can claim double what you owe them (Article 110).

When part of an order is simply running late, the decision is whether to ship what's ready now or wait for the rest. At this point, there's no more waiting time inside your shop: part of the order isn't going to arrive, or you don't know when it will. And that changes what you do with the rest.

First: separate that item from the rest of the order

Before you decide what to do about the missing item, keep that decision separate from everything else. If the other two items in the order are already ready, deliver or ship them now. A missing part is no reason to hold back a cake or a phone case that's been sitting ready on the counter for two days.

Think of the order as three separate items, not one block. What's out of stock affects one item and its cost, not the other two: those keep moving along as normal, and you let the customer know they're ready when it's their turn, without waiting for the third one to get sorted out.

What to do as soon as you find out

When you discover you're out of stock

1Reach out before they ask
As soon as you know something's missing, message them. If you wait for the customer to ask why nothing's arrived, you've already lost control of the conversation, and you've earned their distrust for free.
2Separate out that item's cost
Look at how much that item accounts for within the full order. In a $54 order with the blue vase at $18, that's the number you're going to move, not the other two items'.
3Offer options, not excuses
Don't send a message explaining the mess with your supplier or your storage room. Send concrete options: a substitute, a refund of that $18, or waiting with a firm date.
4Follow through on their choice that same day
If they choose a refund, process it that afternoon, not whenever you happen to remember. A customer waiting on a refund watches their card balance more closely than they ever watched the order.

Substitute, refund, or wait: which path fits

The question of the date is what sorts out the three options. With a short, firm date, you offer to wait. Without a date, the real choice is between a substitute and a refund, and that comes down to whether something truly equivalent exists, not just something that sounds similar.

Without a restock date, offer the substitute before the refund

Path	When to use it	What to say to the customer
Wait	You know the date and it's short: a few days, not "sometime next week, we'll see."	Here's the exact date I'll have it again
Substitute	There's an item with a similar price and function that truly works for what they wanted	I'll swap it for this one, same price, same function
Partial refund	There's nothing equivalent, the item that's out of stock was the whole reason for the order, or you don't know when you'll restock	I'll refund just that $18 and move ahead with the rest

If a substitute costs more, you absorb the difference: it's offered at the same price, or not offered at all. And it's offered, not shipped without asking: the Civil Code doesn't let you force the customer to accept something different from what they bought, even if it's worth the same or more, and consumer law only lets you send it on your own initiative if the customer was expressly told about that possibility beforehand, without raising the price, and with the same quality or better (Article 111). It works best when it keeps whatever matters most to the customer about that item: in two simulated-purchase experiments at an online grocery store, with more than 3,000 households, substitutes that matched the product's main trait, flavor in some cases and brand in others, were accepted more often. In your business that might be a part's size, an ingredient's flavor, or a box's color. If the customer turns it down, move on to the refund without pushing a second alternative, because a third option starts to sound like you don't have a handle on your own inventory.

Save the wait-and-see option for a date that's actually yours, not whatever the supplier says "should" happen. If you don't have it confirmed in writing or backed by an order you've already placed, treat it as if you don't have a date at all, and go straight to a substitute or a refund. If you give a date and miss it, the customer can give you one more deadline, and if that one's missed too, they can cancel the purchase; and if you tell them you're not going to deliver it at all, they can cancel on the spot (Article 66 bis of the same law).

The message, word for word

Hi Maria, your Saturday order is on track, but the blue vase you ordered is out of stock and won't arrive for two weeks. I can send you the same vase in green, at the same price, or refund the $18 for that item and move ahead with the rest of your order as is. Let me know which you'd prefer and I'll take care of it today.

The costly mistake

Refunding the whole order because one piece fell through, or letting the days go by without saying anything, hoping it restocks. The first costs the customer something you actually had ready and already paid for; the second turns an ordinary stockout into a customer who won't prepay you again. In a multi-item order, the one that's out of stock should never hold up the ones that are ready.

With the stockout handled and the rest of the order moving along untouched, the only loose end is the customer having to ask what's going on, and getting ahead of that question is what comes next.

What you walk away with

You know how to separate the out-of-stock item from the rest of the order, which still gets delivered or shipped just as fast.
You have the rule of thumb: wait only with a short, firm date, offer a substitute if a truly equivalent one exists, and issue a partial refund for everything else.
You have the message that offers options without making excuses or explaining the supplier's problem.
You know that if a refund is due, it gets processed the same day you give notice, not whenever you remember.

Three cases to decide

Answer before opening each one. If one gives you trouble, go back to the section that explains it.

1. An $80 order with four items: one item worth $15 is out of stock, and your supplier confirms in writing that it'll be back next Thursday, in six days.

Offer to wait. The date comes from the supplier, it's confirmed in writing, and the timeframe is short, so you can give it to the customer as firm without risking missing it.

2. A customer orders a case for a phone model that's no longer made, and none are left in stock.

Refund the amount for that line. There's no real substitute because the function depends on the exact model, and there's no restock date because the item will never be made again.

3. The main ingredient for a catering dish runs out, but you have another one with a similar flavor and price that covers the same role on the menu.

Offer the substitute before the refund, at the same price. Only if the customer turns it down do you move to refunding that line; don't offer them a second alternative.

With the substitution sorted out, you've still got the customer who asks before you've had time to tell them: that's what the next lesson covers.

Sources

Royal Legislative Decree 1/2007, of November 16, approving the consolidated text of the General Law for the Protection of Consumers and Users and other complementary laws. Boletín Oficial del Estado (Spain's Official State Gazette), consolidated text, accessed October 2026.
Royal Decree of July 24, 1889, publishing the Civil Code. Boletín Oficial del Estado (Spain's Official State Gazette), consolidated text, accessed October 2026.
“Sorry, the product you ordered is out of stock”: Effects of substitution policy in online grocery retailing. Dong Hoang and Els Breugelmans, Journal of Retailing, 2022 (copy in the Leeds Beckett University repository).

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