Hartfield Services Ltd, a £48m UK professional-services firm with 320 staff, runs Sage 200 as its ERP, Salesforce as its CRM and a bespoke time-recording system built in 2016. Revenue recognition is done manually by extracting CSV files from each system, reconciling them in Excel and re-entering totals into Sage. The process takes three days at month end and introduced a £47k error in Q2 2024 that only surfaced at the annual audit. The fix is a modern integration architecture, not more Excel.
API-First Integration
An architecture in which each system exposes a RESTful or GraphQL API, and integrations are built by connecting APIs rather than by extracting and re-importing files. API-first integration is event-driven (a new CRM opportunity triggers a project record in the ERP automatically), reducing manual data entry, eliminating import timing gaps and enabling near-real-time financial reporting. The Competition and Markets Authority mandated API-first connectivity in UK Open Banking, and the pattern is spreading to UK payroll (HMRC RTI) and HMRC MTD.
iPaaS (Integration Platform as a Service)
A cloud-based middleware layer that orchestrates data flows between applications using pre-built connectors and visual workflow design. Leading iPaaS platforms in the UK market include Microsoft Azure Integration Services (Logic Apps + API Management), MuleSoft (Anypoint Platform), Boomi and Workato. For UK SMEs using Sage 200, Xero or QuickBooks, native connector libraries reduce integration build time from weeks to days.
HMRC's Making Tax Digital for Corporation Tax (MTD CT, consultation ongoing as of 2025) will require large UK businesses to maintain digital records and submit quarterly updates directly from software. Finance systems must be MTD-compatible by design — meaning manual journal entry and CSV-based processes will not satisfy the digital-link requirement.
| Integration scenario | Pattern | UK tool option | MTD compliance impact |
|---|---|---|---|
| CRM opportunity to ERP project | API event trigger (webhook) | Azure Logic Apps + Sage API | Revenue recognised in digital records from day one |
| Time-recording to ERP billing | Scheduled batch sync (nightly) | MuleSoft + Sage 200 connector | Eliminates manual journal; satisfies MTD digital link |
| Payroll to HMRC RTI | Direct HMRC API (RTI submission) | Native payroll software (MHR, Moorepay) | Mandatory: non-negotiable statutory requirement |
| Bank feed to ERP reconciliation | Open Banking API (FCA-regulated) | Xero/Sage bank feeds via TrueLayer | Bank statements as digital records under MTD VAT |
Hartfield's IT and finance team design a three-layer integration using Azure Logic Apps: (1) a Salesforce webhook fires when an opportunity moves to 'closed won', creating a project record in Sage 200 via the Sage API; (2) the time-recording system posts approved timesheets nightly via a MuleSoft connector, generating WIP accruals automatically; (3) a bank-feed API from TrueLayer pulls cleared receipts into Sage, triggering automated debtor matching. Month-end revenue recognition drops from three days to four hours and the manual-entry error rate falls to zero in the first two cycles post-implementation.
⚠️Building point-to-point integrations without a middleware layer
→ Direct API connections between every pair of systems create an unmaintainable web of dependencies. A central iPaaS layer adds one abstraction but eliminates N-squared complexity as the system estate grows.
⚠️Ignoring failure modes and reconciliation controls
→ API integrations can fail silently — a timeout or 429 rate-limit response may result in a missing journal entry. Build idempotency keys, retry logic and a reconciliation report comparing source-system totals to ERP totals after every nightly sync.
⚠️Treating HMRC MTD as an IT project rather than a finance-process change
→ MTD requires not just compatible software but a redesigned end-to-end process where every adjustment, correction and period-end entry maintains a complete digital audit trail. Finance teams must own the process design; IT delivers the tooling.