Choosing a Shopify development agency is one of the most consequential decisions in an eCommerce project. The wrong agency builds a store that looks good on the handover call and underperforms for the next three years. This guide covers what a genuine Shopify agency does, how to evaluate one properly, what builds cost, when Shopify is the right platform — and when it is not.
A Shopify development agency builds, customises, and optimises Shopify and Shopify Plus stores — covering theme development, custom app and integration development, platform migration, ERP and CRM integration, and ongoing conversion rate optimisation. To evaluate one properly: ask for Shopify Plus builds with custom functionality (not theme installs), named ERP integrations with specific examples, and client results in terms of revenue and conversion rate — not design awards.
Suggested: Shopify Plus admin dashboard or custom Shopify storefront design
Alt: “Shopify Plus development agency project showing custom storefront design and eCommerce functionality”
A genuine Shopify development agency does significantly more than install a theme and configure products. The distinction between a theme-based Shopify setup and a properly developed Shopify Plus store is the same as the distinction between a template website and a bespoke web application. The work falls into five areas:
Custom Shopify theme development from a design system rather than an off-the-shelf theme. This includes Liquid templating, section and block architecture for merchant flexibility, performance optimisation (Core Web Vitals, LCP, CLS), and responsive mobile-first design. Most agencies install themes. A Shopify development agency builds them.
Shopify’s extensibility model means custom business logic lives in apps and Shopify Functions — not in theme code. Custom apps handle requirements like subscription management, loyalty programmes, custom pricing rules, and B2B account features. Shopify Functions allow custom checkout logic — discount rules, delivery method filtering, payment method conditions — without third-party app dependency.
The most complex and frequently underscoped area of any Shopify build. Connecting Shopify to Sage, SAP, Dynamics, NetSuite, or Epicor requires mapping the order data model to the ERP model, handling partial shipments and back-orders, managing inventory sync without creating stock discrepancies, and building error handling that does not silently lose orders. This is integration engineering, not configuration.
Moving from Magento, WooCommerce, BigCommerce, or a bespoke platform to Shopify. Migration scope includes product and variant data, customer accounts and order history, URL structure and redirect mapping (critical for SEO continuity), payment gateway and subscription data, and content. Each data type has its own migration approach. A clean migration plan specifies all of them before a line of code is written.
A Shopify build that launches and is never touched again will underperform within 12 months. A genuine Shopify agency provides post-launch CRO — using GA4 funnel data, heatmaps, and A/B testing to systematically improve the conversion rate on the store they built. See our guide to eCommerce conversion rate optimisation for the full framework.
The decision between standard Shopify and Shopify Plus affects what is buildable, what it costs monthly, and how much of your checkout you can control. Most businesses generating above £1M annually should be evaluating Shopify Plus specifically.
| Feature | Shopify (standard) | Shopify Plus |
|---|---|---|
| Monthly cost | From £65/month | From £2,000/month (or 0.25% of revenue) |
| Checkout customisation | Limited — Checkout Extensibility read-only | Full Checkout Extensibility — custom UI, logic, discounts |
| B2B features | None native | Company accounts, volume pricing, payment on account (native) |
| Staff accounts | Limited by plan | Unlimited |
| API rate limits | Standard | 10× higher — critical for ERP integration |
| Shopify Flow automation | Not available | Included — order routing, fraud, customer tagging |
| Dedicated support | Standard support only | Dedicated Merchant Success Manager |
| Transaction fees | 0.5% to 2% (unless Shopify Payments) | 0.15% (unless Shopify Payments) |
At £1M annual revenue on standard Shopify with a 2% transaction fee (non-Shopify Payments), the fee cost alone is £20,000/year — approaching the Shopify Plus fee of £24,000/year with a 0.15% rate. Above £1M, Plus almost always makes commercial sense on transaction fees alone, before accounting for the additional functionality.
Shopify is an excellent platform for the right use case. The characteristics of eCommerce businesses that thrive on Shopify:
Shopify Plus is well-suited to businesses in the £500k to £10M annual revenue range. Below that, standard Shopify is typically sufficient. Above £10M with complex pricing or B2B requirements, Adobe Commerce often becomes more appropriate.
Shopify’s checkout experience and native features are optimised for B2C consumer purchasing — single buyer, card payment, standard delivery options. For primarily B2C businesses, Shopify’s native checkout is excellent.
Shopify handles catalogues up to approximately 50,000 SKUs well. Beyond that, performance and navigation complexity can become limiting. Highly complex attribute relationships (configurable products with many variants) are also less elegant in Shopify’s product model than in Magento.
For businesses that need to go live quickly, Shopify’s hosted infrastructure, native payment processing, and large app ecosystem mean a well-specified store can launch within 8 to 12 weeks — faster than a comparable Magento build.
Shopify’s theme architecture and the quality of available design tools make it the strongest platform for brand-first eCommerce. If the visual experience is the primary differentiator, Shopify is the right environment.
Shopify is fully hosted — no server management, security patching, or infrastructure scaling. For businesses without a technical team, this reduces operational risk significantly compared to Magento Open Source.
Shopify is the wrong platform for a specific set of requirements. Choosing it for these use cases leads to expensive custom development that fights the platform architecture — or a rebuild within 18 months when the limits are hit.
| Requirement | Shopify | Adobe Commerce |
|---|---|---|
| Account-level product visibility (shared catalogues) | Custom build required — significant cost | Native in Adobe Commerce B2B module |
| Per-account contract pricing from ERP in real time | Possible via app — complex and fragile | Native — ERP pricing pulled at page load |
| Negotiable quote workflow | No native equivalent — custom build | Native — full request, counter-offer, accept workflow |
| Purchase order approval workflows | Custom build required | Native — configurable multi-level approval |
| 100,000+ SKU catalogue with complex attributes | Performance and navigation challenges | Designed for large, complex catalogues |
| Real-time bidirectional ERP sync with complex logic | API rate limits can constrain high-volume sync | Deep integration capability, higher API limits |
The honest platform assessment: 5MS builds on Shopify Plus, Adobe Commerce, and WooCommerce. We have no platform preference. When a client comes to us with B2B requirements that include shared catalogues, negotiable quotes, and real-time ERP pricing, we tell them that Adobe Commerce is the better fit — even though a Shopify build might be a larger project for us. Platform-agnostic advice is only possible when the agency genuinely builds on all the platforms it recommends. See our Magento B2B features guide for the full comparison.
Shopify development costs vary significantly based on what is being built. The largest variable is always integration scope — ERP, CRM, and third-party system connections. Any agency quoting integration costs without a discovery phase is estimating, not scoping.
| Build type | Typical cost range | What is included |
|---|---|---|
| Standard Shopify (theme-based) | £5,000 – £15,000 | Theme customisation, product upload, payment and shipping configuration, basic apps. No custom development. |
| Shopify Plus (custom theme, no integration) | £15,000 – £35,000 | Custom theme development, Checkout Extensibility configuration, Shopify Flow setup, standard app integrations. |
| Shopify Plus (with ERP integration) | £35,000 – £80,000 | Custom theme, ERP integration (inventory, order sync, pricing), custom app development for business logic, discovery phase. |
| Shopify Plus (complex: migration + ERP + custom apps) | £80,000 – £150,000+ | Full custom development, ERP and CRM integration, platform migration with data mapping, custom Shopify Functions, performance programme. |
| Ongoing retainer (post-launch) | £2,000 – £8,000/month | CRO, A/B testing, feature development, SEO, paid media, email marketing. Scope varies by service mix. |
A paid discovery phase (typically £3,000 to £8,000) produces a detailed specification covering integration scope, data mapping, custom functionality requirements, and a realistic fixed-price build quote. Skipping discovery on a build with ERP integration is the most reliable way to produce a project that runs 40 to 80% over budget. The discovery cost is always recovered in build cost accuracy.
Build timelines in Shopify development are frequently underquoted. The most common causes of timeline overrun are: incomplete content and product data at build start, ERP integration complexity that was not scoped in discovery, and slow client feedback cycles on design and UAT.
Theme customisation, product upload, payment and shipping configuration. No custom development, no ERP integration, catalogue under 5,000 SKUs, content ready at project start.
Custom theme development, Checkout Extensibility, Shopify Flow, standard app integrations. No ERP integration. Includes design phase, build, and UAT.
Adds integration discovery, API mapping, bidirectional sync development, error handling, and integration UAT to the build timeline. ERP integration phase typically adds 8 to 12 weeks.
Platform migration adds data mapping, migration scripts, redirect mapping, and parallel running to the timeline. Migration from Magento or a bespoke platform typically adds 6 to 10 weeks.
The timeline killer: content and product data readiness. The single most common cause of Shopify build overruns is a client who is not ready with product images, descriptions, and data at the point the build team needs it. Establish a content delivery schedule at project kick-off and treat it as a critical path dependency — because it is.
Suggested: Shopify Plus store example or agency team working on eCommerce build
Alt: “Shopify Plus development agency building custom eCommerce store with ERP integration”
Most Shopify agencies look identical in their marketing. The differences emerge in what they have actually built and whether they can demonstrate specific technical capability. Seven questions that separate genuine Shopify development agencies from those that primarily install themes and configure apps:
Not a theme install. Not an app configuration. Custom Shopify Functions or a private app built to solve a specific client requirement. If they cannot show you one, they have not built one.
The right answer names specific ERPs, describes the data mapping approach, and mentions specific edge cases — partial shipments, credit limit enforcement, multi-warehouse inventory. Vague answers about “API integration” indicate limited integration experience.
A genuine discovery phase produces: a technical specification, data architecture diagram, integration scope document, and a fixed-price build quote with clear scope boundaries. An agency that does not offer a paid discovery phase is not scoping complex projects properly.
Design awards are not conversion rate improvements. If an agency cannot give you specific CVR data from their Shopify builds, they are either not measuring it or do not have enough data to share. A genuine full-service Shopify agency tracks this.
Get the names. Ask for their LinkedIn profiles. Ask which of their Shopify Plus builds they worked on. Agencies win projects with senior people and sometimes deliver with junior people. Know who is building your store before you sign.
A Shopify build that launches and receives no post-launch investment will underperform within 12 months. An agency that has no post-launch service offering is not structured to help you grow — only to build and move on.
How the agency handles scope changes tells you more about the working relationship than the proposal does. A clear change control process, written into the contract, protects both parties. An agency that does not have a change control process will resolve scope disputes differently each time.
ERP integration cost cannot be quoted accurately without a discovery phase. Any agency giving a fixed price without one is guessing — and the risk lands on you when the scope expands.
Installing a Shopify theme and configuring it is not development. A development agency should show custom Liquid code, private apps, or Shopify Functions in their portfolio — not Debut or Dawn theme customisations.
Shopify Plus builds with ERP integration take 20 to 32 weeks when done properly. An agency quoting six to eight weeks either has not scoped the integration or is planning to cut corners on testing.
A Shopify build that launches at 1% conversion rate and receives no CRO investment will stay at 1%. An agency that treats launch as the endpoint has not thought about the commercial outcome — only the delivery.
Design awards do not measure revenue, conversion rate, or technical robustness. They measure how a store looks to a design jury. Ask for business results, not trophies.
Scope changes are inevitable on complex Shopify builds. An agency without a documented change control process will handle them inconsistently — sometimes charging, sometimes absorbing the cost, always creating ambiguity.
5MS is a full-service eCommerce agency based in Wolverhampton, UK. We have been building eCommerce stores since 2011 — on Shopify Plus, Adobe Commerce (Magento), and WooCommerce. We are an Adobe Solution Partner and a Shopify development agency. We are not platform-exclusive to either.
Platform-agnostic means we recommend the platform that fits the business requirements, not the one that is most convenient for us to build on. When Shopify Plus is the right choice — mid-market B2C, strong brand requirements, speed to market, manageable catalogue — we build on Shopify Plus and we build it properly. When the requirements go beyond what Shopify handles well — complex B2B, large catalogue, real-time ERP pricing, shared catalogue visibility — we say so and recommend Adobe Commerce instead.
Full custom Shopify Plus development — theme from design system, Checkout Extensibility, Shopify Functions, private app development, ERP and CRM integration.
Full migration service covering product and variant data, customer and order history, URL mapping and redirects, payment and subscription data, and content.
Bidirectional ERP integration covering inventory, order sync, pricing, and customer data. Scoped after discovery, not before. 5MS has integrated with all major UK ERP platforms.
Post-launch growth programme covering conversion rate optimisation, technical SEO, Google Shopping and Meta paid media, and Klaviyo email marketing — all connected to the Shopify store we built.
Our guarantee on platform advice: if you come to 5MS asking for a Shopify build and we believe Adobe Commerce or WooCommerce is a better fit for your requirements, we will tell you — with specific reasons. We have had this conversation dozens of times. The clients who trust our platform recommendation stay with us longer and get better commercial results than those who were sold a platform that was not right for them.
- A Shopify development agency does far more than install themes. Custom app development, Shopify Functions, ERP integration, platform migration, and post-launch CRO are what separate a development agency from a theme configurator.
- Shopify Plus is the right choice for mid-market B2C eCommerce with strong brand requirements, catalogues under 50,000 SKUs, and standard checkout requirements. It is not the right choice for complex B2B with shared catalogues, negotiable quotes, or real-time ERP pricing.
- Costs range from £5,000 for a standard theme build to £150,000+ for a complex Shopify Plus build with ERP integration and platform migration. The largest variable is always integration scope — never accept a fixed price for ERP integration without a discovery phase.
- Seven questions separate genuine Shopify agencies from those that say they are one. Custom Shopify Functions, named ERP integrations, discovery process detail, client CVR data, named developers, post-launch CRO services, and change control process.
- Platform-agnostic advice requires genuinely building on multiple platforms. An agency that only builds on Shopify will always recommend Shopify. Work with an agency that builds on Shopify Plus, Adobe Commerce, and WooCommerce — and can tell you honestly which one fits your requirements.
Tell us what you sell, what your ERP runs on, and what your requirements are. We will tell you straight whether Shopify Plus, Adobe Commerce, or WooCommerce is the right fit — with specific reasons either way. No platform bias. No sales pitch.
When choosing a Shopify development agency, look for: a portfolio of Shopify Plus builds with custom Shopify Functions or private app development (not theme installs); named ERP integrations with specific examples; a paid discovery phase before any fixed-price quote on complex builds; client results in conversion rate and revenue terms; named developers on your project; and a post-launch CRO and growth programme. Red flags include fixed-price ERP integration without discovery, six-week timelines for complex builds, and design awards presented as evidence of commercial performance. A genuine Shopify development agency also tells you honestly when Shopify is not the right platform for your requirements.
Related guides from 5MS:
Common questions about Shopify development agencies. Get in touch if yours is not here.
We scope eCommerce projects every week across Shopify Plus, Adobe Commerce, and WooCommerce. Tell us your requirements and we will tell you which platform fits — and what the build costs.