Shopify is generally very good at taking care of the complicated bits of ecommerce for you. That's one of the reasons I like working with it.
But every now and then I'll come across a checkout problem where the behaviour looks completely baffling until you find one tiny setting buried somewhere in the Shopify admin.
Here are five worth checking before assuming something is seriously broken.
1. VAT is wrong? Check whether Shopify thinks it's a physical product
I came across this one recently and it's a good example of how one innocent-looking product setting can have consequences elsewhere.
If you're selling a physical item, make sure Shopify actually knows that it is one.
Open the product in Shopify and look in its shipping settings for:
This is a physical product
If that isn't selected, Shopify treats the item as a digital product. That can affect the tax treatment applied at checkout.
Shopify specifically lists this as something to check when taxes aren't being charged correctly.
It's particularly easy to miss if a product has been duplicated, imported or created through another system.
While you're there, check the product category too. Shopify can use its product taxonomy when determining the appropriate tax treatment, so an incorrect or unconfirmed category can produce equally confusing results.
Quick check: Product → Shipping → This is a physical product, then check the product category.
2. Customers in the Isle of Man aren't being charged VAT
This was a particularly interesting one I dealt with recently.
A client noticed that a customer in the Isle of Man hadn't been charged VAT — and looking back, the same thing had happened on several previous orders.
The confusing part is that although the Isle of Man isn't actually part of the United Kingdom, HMRC treats it as part of the UK for VAT purposes. For most ordinary supplies, the VAT rules are therefore broadly the same as for a UK customer.
Shopify, however, can treat the Isle of Man as a separate region when configuring Markets and tax behaviour.
In this particular store the Isle of Man wasn't included in the UK Market, so the first part of the fix was:
Settings → Markets → United Kingdom
and adding the Isle of Man to that Market.
I then checked:
Settings → Taxes and duties
and for this store's tax configuration I needed to explicitly configure the appropriate Isle of Man tax rate there as well.
After that, test the checkout using an Isle of Man delivery address rather than assuming the Market change alone has fixed it.
One important caveat: don't blindly copy a 20% override from somebody else's Shopify store. There are some reduced rates and exceptions, and different Shopify tax configurations behave differently. The important lesson is to check both Markets and Taxes and duties when a particular destination isn't behaving as expected.
3. One product has the wrong VAT rate? Look for an old tax override
This is another setting that's easy to forget exists.
Shopify allows you to override its normal tax calculation for particular products or collections. That's useful when you genuinely sell products with different tax treatment.
The problem comes six months later when nobody remembers the override is there.
You can change a product's category, update the theme and stare at the checkout for half an hour wondering why Shopify keeps charging the "wrong" amount.
The override wins.
Check:
Settings → Taxes and duties
and review any product or collection tax overrides for the affected region.
Shopify confirms that tax overrides take precedence over its product-category tax calculations, so this is high on my list when just one group of products is behaving strangely.
4. The products look right but the shipping VAT doesn't
Product tax and shipping tax aren't necessarily the same thing in Shopify.
Shopify supports separate tax overrides for shipping, and product overrides don't automatically change the tax treatment of the delivery charge.
It can get even more confusing when a basket contains products with different tax rates. Depending on the tax rules for the region, Shopify can calculate shipping tax proportionally across the items in the order.
The result can be a shipping VAT figure that initially looks like a calculation error but is actually deliberate.
So if the merchandise is being taxed correctly but the delivery charge looks odd, check the shipping tax configuration separately rather than changing the products.
Quick check: Settings → Taxes and duties → check the relevant region and any shipping overrides.
5. VAT is missing for just one customer? Check the customer
If everybody else's checkout looks fine but one particular customer isn't being charged the tax you expect, the problem might not be the product or checkout at all.
Shopify supports tax-exempt customers and, importantly, a customer exemption can take precedence over other tax settings.
Open the customer record and check whether a tax exemption has been applied.
This is especially worth looking at when the customer has been in Shopify for a long time, was imported from another system, or has previously been set up for B2B purchasing.
If it's a business customer, don't simply remove an exemption because it looks suspicious — establish why it was applied first.
Test the actual checkout
The common thread with all of these is that Shopify's checkout is affected by more than one part of the admin.
Products, product categories, Markets, customer records, tax registrations and overrides can all influence the final result.
So when I change something, I don't just save the setting and assume it's fixed. I'll normally run a test checkout using the same type of product, destination and customer circumstances that exposed the problem in the first place.
And if it's a tax issue, there's an important distinction between "Shopify is configured incorrectly" and "what tax should legally be charged?"
I can help with the first one. If there's any uncertainty about the second, that's a question for your accountant or tax adviser.