# API Integration Developers UK

Source: https://dijituldevelopments.co.uk/api-integration/
Updated: 2026-10-10

> dijitul developments builds API integrations for UK businesses: connecting accounting software, ecommerce platforms, CRMs, payment providers and in-house systems so orders, invoices, stock and customer records move automatically instead of being retyped. We've been building integrations since our KashFlow and OpenCart days. Every project is a fixed-price quote after a free chat.

## Problems this solves

- Staff retype every web order into Xero, Sage or QuickBooks by hand
- Stock levels on the website, the marketplace and the warehouse never agree
- An off-the-shelf connector syncs most things, but not the one field you need
- An old integration stopped working after a provider changed its API and nobody knows how it was built
- Nobody is told when a sync fails, so problems surface weeks later as accounting errors
- Three spreadsheets hold the same customer list and they all disagree

## Key facts

- We have built integrations since around 2011, starting with a full KashFlow and OpenCart integration later ported to Magento
- We work with REST, GraphQL, SOAP and webhook-based APIs, and with file feeds (CSV, XML, SFTP) where no API exists
- OAuth 2.0 token handling is built in: Xero access tokens expire after 30 minutes, so refresh logic is not optional
- Every integration runs through a queue with retries, idempotency keys and a log you can read
- We design around each provider's rate limits rather than discovering them in production
- You own the code and the data at the end of the project
- Fixed-price quote after a free chat and a short scoping stage

## What API integration actually means for your business

An API (application programming interface) is the door a piece of software leaves open so other software can read and write its data. Xero, Shopify, Stripe, HubSpot, Microsoft 365 and most modern systems have one. API integration is the code that walks through those doors on your behalf: it takes a paid order from your shop, creates the customer and invoice in your accounts, marks it paid, reduces stock and tells the warehouse, without anyone touching a keyboard.

The business case is usually simple. If someone spends an hour a day copying data between systems, that is several hundred hours a year of work that adds no value and introduces typing errors. A good integration removes the copying and, just as importantly, makes the data trustworthy again because there is one source of truth for each record.

We've been doing this since around 2011, when we built a full KashFlow and OpenCart integration that created customers automatically, raised invoices on payment, kept stock and prices in step and issued credit notes for cancelled orders. The APIs have changed since then. The principles have not.

## The integrations we build most often

Most of our integration work falls into a handful of patterns. Each has its own page with the technical detail:

- **Accounting:** Xero, QuickBooks Online, Sage and KashFlow, usually pushing sales invoices and payments in and pulling payment status out. See our overview of accounting software integration.
- **Payments:** Stripe and other payment gateways, including Strong Customer Authentication, refunds and reconciliation.
- **Ecommerce and stock:** Shopify, WooCommerce and OpenCart linked to an ERP or warehouse system (ecommerce to ERP integration) and to marketplaces such as Amazon and eBay.
- **Sales and customers:** CRM integration so leads, quotes and orders appear in the right place.
- **Office tools:** Microsoft 365 through Microsoft Graph, for calendars, SharePoint files and Teams notifications.
- **Smaller pieces:** postcode lookup, punch-out (OCI) catalogues for selling into large companies' procurement systems, and custom webhooks.

When there is no API to connect to, we build one. When several systems need to work as one, that is systems integration, which is the same craft at a larger scale.

## How we build integrations that keep working

Connecting two APIs for a demo takes an afternoon. Building one that still works after a provider outage, an expired token or a customer with an apostrophe in their name takes engineering. These are the parts we treat as standard, not extras:

- **Token management.** Most accounting and SaaS APIs use OAuth 2.0. Xero access tokens last 30 minutes; Intuit issues a new QuickBooks refresh token on each refresh, which must be stored or the connection breaks. We encrypt tokens at rest and refresh them before they expire.
- **Queues and retries.** Every outbound call goes on a queue (Redis with Laravel Horizon, or a database queue for smaller jobs). If an API is down or returns HTTP 429, the job waits and tries again with exponential back-off instead of failing silently.
- **Idempotency.** If a job runs twice, it must not create two invoices. We store external IDs against your records and, where the API supports it (Stripe accepts an `Idempotency-Key` header on every POST request), send a key with each create.
- **Rate limits.** Xero allows 60 calls per minute per connected organisation, and its developer pricing page sets the daily cap per organisation (1,000 or 5,000 calls) by the app's pricing tier. QuickBooks Online allows 500 requests per minute per company. We batch, cache and schedule around these numbers.
- **Logging and alerts.** Every sync is written to a log you can search. Failures that need a person raise an alert with enough context to fix them.

## Custom integration or an off-the-shelf connector?

We are not precious about writing code. If Zapier, Make, a Shopify app or the accounting package's own app marketplace does exactly what you need, use it and save the money. We'll say so in the first chat.

Custom integration makes sense when:

- your process has rules a generic connector cannot express, such as splitting one order into invoices for two companies, or applying trade pricing by customer group;
- you need to integrate with something bespoke, legacy or obscure that has no listed connector;
- volumes push per-task pricing on automation tools higher than owning the code would cost;
- you need an audit trail, GDPR controls or error handling that a no-code tool cannot give you;
- a chain of connectors has grown so tangled that nobody can tell which one changed a record.

Sometimes the answer is a mix: a no-code tool for simple notifications and custom code for the money-handling parts. We'll also consider workflow automation tools like n8n where they fit.

## Our process and what you own

Integration projects follow the same path as all our work:

- **Free chat.** You tell us which systems you use and where the manual work is. We tell you honestly whether custom code is the right answer.
- **Scoping.** We look at the APIs involved, test access with sandbox accounts, and write an integration map that says which system owns each piece of data. This is where rate limits, missing fields and API costs come out.
- **Fixed-price quote.** A defined scope at a fixed price, or a phased plan if the work is large.
- **Build and test.** Built against sandbox environments first, then run in parallel with your manual process until the numbers match.
- **Handover.** You own the code and data. We document the integration so any competent developer could maintain it.

Integrations need looking after: APIs change versions and providers retire endpoints. Ongoing monitoring and updates are available through our sister company dijitul support. If you are moving data out of an old system as part of the work, see data migration.

## What we deliver

- A written integration map: which system owns which data, which direction it flows and how often
- Connector code for each API, with OAuth 2.0 token storage and refresh
- A queue-based sync engine with retries, back-off and idempotency so nothing is created twice
- Webhook receivers with signature verification for real-time events
- An admin screen showing every sync, its status and any error, with a retry button
- Email or Slack alerts when something needs a human
- Documentation and handover, so another developer could pick it up

Technologies: REST APIs, OAuth 2.0, Webhooks, Laravel, Node.js, Redis, PostgreSQL, Docker

## FAQs

### How much does an API integration cost?

It depends on how many systems are involved, how much data moves and how complex the business rules are. dijitul developments does not publish rates: we have a free chat, scope the integration properly, then give you a fixed-price quote for a defined piece of work so you know the cost before anything is built.

### Can you integrate with a system that has no API?

Often, yes. Many older systems can export or import CSV or XML files, expose a database we can read safely, or accept files over SFTP. Where none of that exists, we can sometimes build a small API layer in front of the system. dijitul will tell you in scoping what is realistic and what the risks are.

### What happens when one of the connected systems is down?

Our integrations queue every change. If Xero, Shopify or another API is unavailable or rate-limiting us, the job waits and retries with increasing delays. Nothing is lost and nothing is created twice, because each record carries an idempotency key or a stored external ID. If retries run out, someone is alerted with the details.

### Should we use Zapier or Make instead of a custom integration?

If a no-code tool does what you need reliably, use it. Custom integration is worth it when your rules are too specific, the volume makes per-task pricing expensive, you need proper error handling and audit logs, or the system you need has no connector. dijitul will give you an honest view in the first chat.

### Who owns the integration code?

You do. When dijitul developments finishes an integration, the code, the documentation and the data belong to your business. You can host it where you like and have any developer maintain it. Hosting and ongoing support are available through our sister companies if you want them, but there is no lock-in.

### How long have you been building integrations?

Since around 2011. dijitul's early integration work included a full KashFlow and OpenCart integration covering automatic customer creation, invoices on payment, stock and price sync and credit notes for cancellations, later ported to Magento. We also built punch-out catalogue integrations for procurement systems. dijitul has traded since 2006.

### Which technologies do you use for integrations?

Mostly PHP 8 with Laravel, or Node.js with TypeScript, backed by MySQL or PostgreSQL and Redis queues, deployed in Docker. We pick the stack that suits your existing systems and whoever will maintain the code. The patterns matter more than the language: queues, retries, idempotency, token refresh and logging.

## Pricing and contact

Every project gets a fixed-price quote after a free initial chat and a short scoping stage. You own the code and the data. Book a free chat: https://dijituldevelopments.co.uk/contact/ · 01623 650333 · info@dijitul.uk