In August 2026, 28.8 percent of retail sales by value in Great Britain were made online, on the first estimate from the Office for National Statistics. That is the share of all retail spending, in stores and online combined, for that one month: close to three pounds in every ten. With that much money passing through online checkouts, the question of which ad earned which order is worth settling against your own records rather than the platforms'. Before any agency can do its job in your store, or be judged on it, your own records need to be complete: a cost on every product, orders you can match against ad platform reports, a customer list with consent on record, and accounts in your name. Most of this article is about getting those records ready.
Why your own records come first
An agency reports from the tools it runs, and those tools count in different ways. Google Ads counts a purchase for 30 days after a click by default when you create a new conversion. Its default attribution model for most conversion actions is data-driven, which distributes credit between ad interactions using your account's past data. Shopify offers its own choice. Its marketing reports support last non-direct click, last click, first click, any click and linear models, and Shopify says the any-click model gives out more credit than the orders you received.
None of these numbers is wrong. They answer different questions, which is why a platform total and your order count can disagree. Apple adds a second gap. Since iOS 14.5, apps must ask permission before tracking you across other companies' apps and websites, and an app that is refused cannot use the advertising identifier. The rule covers apps on iPhone, iPad and Apple TV, and it bites only where tracking has not been allowed. We infer that an app-based ad platform may then see fewer of the purchases its ads helped cause.
Your store records and your product costs are the one yardstick you control, which is why the first job sits with you.
Know your margin on every product
Shopify's profit reports work out gross margin as net sales minus cost, divided by net sales, and only for variants that had a cost recorded when they sold. Costs you enter today therefore count for future sales, not past ones. Discounts and refunds also change the margin you see, so read it after both.
To check your side, open the Gross profit by product report. Shopify says that if orders are missing from it, those variants probably have no cost recorded. Add the cost to every variant that sells but is missing from that report. An agency uses those margins to set a break-even return on ad spend (ROAS) and to drop products that cannot carry ad costs. What you end with is a margin table by product, with no best-seller missing a cost.
Reconcile what the platforms say with what the store says
Pick one recent month. Put the purchases each ad platform reported beside your Shopify orders for the same dates and write down the gap. Shopify itself says you can use the any-click model to reconcile attribution reported by each channel. Our inference from that: when several platforms each claim the same sale, their claims can add up to more than your orders.
An agency can then report store net sales first, platform figures second, and treat the gap as an agreed conversion factor. Done properly, this leaves one month of platform purchases beside store orders, with the gap written at the top.
Check your customer list and the consent behind it
An agency will want to market to people who have already bought, and the rules differ by country. In the UK, regulation 22 of the Privacy and Electronic Communications Regulations stops you sending marketing email to individuals unless they have consented, or they are existing customers who bought something similar and were offered a simple opt-out when you collected their details and in every message. The Information Commissioner's Office says the same rule covers texts, and it has flagged that its guidance is under review after the Data (Use and Access) Act.
In the US, the Federal Trade Commission says the CAN-SPAM Act covers a message to former customers announcing a new product line, and that a sender must honour an opt-out request within 10 business days. These are different regimes, so a list built for one country is not automatically right for the other.
To check yours, export your customers from Shopify. Its customer file uses a yes or no field for Accepts Email Marketing, and Shopify warns that you should only send marketing emails to customers who have opted in. A yes or no flag does not show where or when someone agreed, so keep the sign-up form wording and dates yourself. Welcome and win-back emails should go only to addresses with consent, with opt-outs suppressed. The file to keep is the export, the count of yes flags, and the sign-up wording and dates for each source.
Put every account in your name
Write down every account the agency will touch: the store, each ad account, the product feed, analytics, the email platform, the domain and the creative files. You should be an admin on each, and the agency should hold a role you can remove. On Shopify, collaborator access can be managed and removed from your admin, and the partner must use two-step authentication to log in.
On Google Ads, the admins of a manager account that has ownership of your account can edit user access, managers and product links within it, and the admin of your own account is the one who grants that ownership. Ask which set-up the agency plans to use. Ask, too, whether the creative files you pay for are yours when you stop, and expect requests for access rather than passwords. The output is one list: every account, you as admin, and the agency's removable role beside it.
Decide what the report must say
Write the report specification before your first meeting, then ask each agency for a sample from another ecommerce client with the names removed. Look for Shopify net sales first, with platform-reported sales beside it. Look for new and returning customers shown separately, and for margin after discounts and refunds. Insist on the gap from your reconciliation being shown every time, not hidden.
Set a monthly full review and a weekly look at spend, orders and stock. If you are unsure which single figure should lead, our post on which marketing number actually matters explains how to pick the one nearest to a sale.
Check stock and the offer before spending
An ad that sells what you cannot ship wastes the budget and annoys the customer. Confirm that your stock figures are right for the products you want to push, and agree who pauses ads when a line runs low. Write down who updates the ad, the landing page and the email when an offer changes, so all three say the same thing on the same day. An agency that asks about stock, delivery times and returns terms before it writes a single ad has read that note.
What to ask an agency once you are ready
Ask to see a reconciliation of platform purchases against store orders from another Shopify store, with the names removed. Ask how it sets a target return from a margin like yours, and which products it would leave out. Ask which of your sales the ad platforms cannot see. Ask how it would report new customers separately from returning ones, and what it would do first if your reconciliation gap turned out to be wide.
Ask about the Shopify Partner Directory too. Shopify says partners listed in the directory work independently, and that they sit in Select, Plus, Premier and Platinum tiers based on factors including their experience and proven success on Shopify. A tier is a reason to ask more questions, not an answer. The same page tells you to check reviews, work samples and certifications before you choose.
Until your margins exist, a month of your own data work beats a retainer; an agency earns its fee once you have the yardstick and need creative, media buying or email at volume, the paid media and email work for ecommerce brands that we and other agencies sell. If you do hire, make the first month's goal about data rather than sales: the margin table finished, the reconciliation gap agreed and the access sorted.
Three things to do this week
First, add cost per item to your ten best-selling products, including every variant, and open the Gross profit by product report to confirm each one shows a margin. Second, take last month and put each platform's reported purchases beside your Shopify orders, then write the gap at the top of a page. Third, list every account an agency would need and who is admin on each, and export your customer list to see how many addresses carry a yes. Do them in that order. By Friday you will have a margin, a gap and a map of who owns what, and any agency you meet next can be tested against them.
Once the three tasks above are done, tell us about your business with the margin table, the gap and the account map attached.
↳ Frequently asked
01What if my Shopify store never recorded product costs for past sales?
Shopify's profit reports only count variants that had a cost recorded when they sold, so costs you add now apply to future sales and past margins stay blank. Add a cost to every selling variant today and judge any agency on the months that follow. For earlier months, supplier invoices can give you an estimate, as long as you label it as one.
02Why does Google Ads report different sales from my Shopify orders?
The two count by different rules. Google Ads counts a purchase for 30 days after a click by default on a new conversion and uses a data-driven model for most conversion actions. Shopify lets you choose between last non-direct click, last click, first click, any click and linear, and says any click gives out more credit than the orders you received. Compare one month of platform purchases with your orders, record the gap, and ask your agency to report it every time.
03Can I email last year's Shopify customers about a new range?
It depends on where they are. In the UK, marketing email to individuals needs their consent, or the existing-customer exception, which needs a similar past purchase and an opt-out offered when you collected their details and in every message. In the US, the CAN-SPAM Act covers email to former customers announcing a new product line, and an opt-out must be honoured within 10 business days. The two regimes differ, so check the rule for each country your customers live in.
04Does a Shopify Partner Directory listing mean an agency suits my store?
No, treat it as a prompt for questions. Shopify says listed partners work independently and are placed in Select, Plus, Premier or Platinum tiers based on several factors, including experience and proven success on Shopify. The directory page also tells you to check reviews, work samples and certifications. Then judge the agency on a reconciliation of platform sales against store orders from another client.