APIs, connectors and middleware that move records between accounting, CRM, payment and messaging systems
API and system integration connects the software a business already runs, such as QuickBooks, Xero, Stripe, WhatsApp Business and an existing CRM or ERP. It covers secure APIs, webhooks, middleware and data synchronisation, so a record is entered once and then reaches each system that needs it. Nobody retypes it.
- Every field is mapped before code.
- Retries, failure alerts and reconciliation are built in.
- Accounts, credentials and source code stay yours.
The work covers the systems most small and mid-size businesses run, including accounting ledgers, marketplace and dealer portals, payment gateways, wallet and bank-transfer collections, courier partners and WhatsApp Business. On-premise software with no API is in scope too. Some projects are a first connection between two systems. Others repair an older connector that drops records without any alert, leaving the accounts team to find the gap at month end.
Where Duplicate Data Entry Builds Up Between Systems
Records Copied Between Two Screens
Staff keep the portal open beside the billing screen and copy customer name, item code and quantity across by hand. The second system runs a step behind. Stock gets promised twice, and dispatch works from a figure that has already changed.
Changes That Do Not Reach the Second System
A customer corrects a delivery address or tax ID in the portal, or a rate is revised in the ERP, and the other system quietly keeps the old value. The invoice goes out wrong. A credit note repairs it later.
Syncs That Fail Without an Alert
A connection breaks overnight. With no alert, retry or log to show it, nobody finds out until a customer phones to ask why an order is still marked “packed”.
Payments Reconciled by Hand
Gateway settlements, wallet credits and bank statements are matched to invoices by hand, so receipts are posted days late and the ageing report misleads the collections team. Paid customers still get reminders. That erodes trust fast.
Older Software With No Interface
The item master, pricing or customer history sits inside an on-premise application that offers no modern interface. Staff fall back on CSV exports. Those are already out of date by the time someone opens the file, and stale copies spread.
Head Office and Branch Systems Kept Apart
Each location runs its own copy of the billing or accounting software, and a revised price list is typed in again at every counter. Two branches quote different rates to the same dealer. Credit holds never arrive.
Enquiries That Reach No Central System
Website forms land in a shared inbox, WhatsApp enquiries sit on one phone and listing-portal leads stay in a vendor panel, so none of them reach the CRM. Follow-up depends on who remembers. Some leads are never called.
Most of these cases do not need a new system at all. They need the existing systems to exchange the same record, in the same format, at the right time, and to report a failure the moment one occurs.
Integration Built Around the Systems Already in Use
Existing software is connected, not replaced. The work starts by reading live data and agreeing what each field means in both systems, before a connector, middleware layer or API moves a single record. Retries, logs and daily reconciliation come with it. The client can check all three without a developer.
One Agreed Record Format
Field-to-field mapping comes before any code. It records which system is master for price and which for stock, what a blank value means, and which side wins when two systems disagree.
Retries and Failure Queues
Network drops, expired tokens and vendor downtime are treated as ordinary events, so messages are retried and duplicates are blocked by a unique key. Anything that still fails waits in a queue. A named person is told.
Logs and Reconciliation
Every transfer leaves a log line naming where it came from, where it went and whether it landed, while a nightly check matches record counts and value totals between the two systems. It shows exactly what moved and what did not.
What Changes When Systems Exchange Data
Focus on business value before discussing technology.
One Entry Used in Every System
An order, lead or receipt is captured once, then passed on to billing, accounts and dispatch without anyone opening a second screen to type it again. Retyping stops.
Changes Carried to Connected Systems
An address correction, rate revision, order status or payment is updated in one system and passed to the others on the schedule agreed for that record type. Decisions rest on a current copy. Stale exports stop circulating.
Alerts When a Connection Breaks
When a connection fails or a vendor changes an API, a named person is told which record is affected and why, in an email or a WhatsApp message. Problems stop waiting for a customer complaint.
Retries for Temporary Outages
A gateway or portal goes down briefly. Pending messages are held and retried automatically, so the record is never dropped and nobody has to find it and send it again by hand.
Existing Software Stays in Use
The accounting package, the counter billing software and the dealer portal keep running the way the team already knows them, with the connection added around them. No migration happens unless the client asks for one.
A Record for Every Message
Any invoice, payment or status update traces back to the message that created it, with its source, time and response. That settles a dispute quickly when a courier, gateway or dealer challenges an entry.
What API and System Integration Includes
Everything required from operational discovery to production deployment and long-term maintenance.
Integration Audit and Data Mapping
Both systems, their live data and their existing interfaces are examined first. The records, fields, direction of flow and ownership rules that the integration must respect are then written into one mapping document both teams can sign.
Custom API Design and Development
REST and webhook APIs are built for the client’s own applications, with authentication, versioning, rate limits and error codes. Written documentation lets other vendors work against them without asking us. Each endpoint is described in OpenAPI.
ERP and Accounting Integration
Two-way connections with QuickBooks, Xero, Zoho Books, Odoo and custom ERPs cover masters, vouchers, stock movements and outstanding balances. The ledger and voucher structure stays. Auditors see what they expect.
CRM and Sales System Integration
Leads from the website, WhatsApp and listing portals flow into Zoho CRM, Salesforce, HubSpot or a custom CRM, with duplicate checks, owner assignment and status write-back built in. Sales sees one list.
Payment Gateway and Reconciliation
Stripe, PayPal, Adyen and wallet or bank-transfer collections are linked to invoices, settlement files are parsed, and receipts are posted against the right invoice. Unmatched credits are flagged for the accounts team.
WhatsApp, Email and SMS Integration
WhatsApp Business API, transactional email and SMS are connected to business events such as a confirmed order or a raised ticket. Delivery and read status returns to that same record.
E-commerce, Marketplace and Logistics
Storefront and marketplace orders are pulled into the client’s system, and courier partners are connected for waybill generation, pickup requests and tracking updates that flow back to the customer. Shipping labels print automatically.
Middleware, Webhooks and API Gateways
A queued middleware layer receives events, transforms formats, throttles calls and holds failures, so neither system is exposed to the other’s downtime. One outage no longer stops two applications.
Legacy and On-Premise Integration
Older applications are reached through database views, ODBC, scheduled file exchange over SFTP or a small secure agent installed on the server. The software staff use daily is left undisturbed.
Multi-Location Data Consolidation
Branch, plant or campus systems feed one consolidated store, either live or on a schedule. Location tags let a manager split the figures back apart by branch. Head office sees every site.
Workspace and Document Integration
Google Workspace and Microsoft 365 connections cover calendars, shared drives and mail, Google Maps handles address and delivery-area checks, and e-signature services support contracts and approvals. Documents land in the right folder.
Monitoring, Alerting and Support
Dashboards show sync health, and alerts cover failures and credential expiry, so a lapsed token is caught before it stops a flow. A support arrangement handles vendor API changes, including the ones announced at short notice, so a deprecated endpoint never surprises the team.
Where API and System Integration Is Used
Real-world business processes we configure and automate.
Distributor With Marketplace and Portal Orders
A distributor sells through two marketplaces, a dealer portal and phone orders, and the back office retypes each order into billing and then into the accounts. Integration pulls orders as they are placed, creates the sales entry against the correct ledger and stock item, and returns the invoice number to the channel.
Clinic Network With Bookings and Billing
A multi-centre clinic takes bookings on its website and by phone, registers patients again at the counter and sends confirmations by hand. Integration passes the booking, patient reference and doctor to billing the moment the slot is confirmed, then sends the WhatsApp confirmation and records whether it was delivered.
Manufacturer With a Field Service App
Service engineers close jobs in a mobile app, yet the ERP is updated days later from paper job cards. Late entries delay invoices. Integration posts job completion, parts used and warranty status as each visit closes, and invoicing and spare-part stock then follow that same record.
Professional Firm With Enquiries From Several Channels
An advisory firm gets enquiries through its website, WhatsApp and a listing portal, and a different person checks each channel. Integration routes all three into one CRM, with duplicate detection and automatic owner assignment so that no enquiry waits unclaimed. Every enquiry gets an owner.
Logistics Operator With Multiple Payment Modes
A transport operator collects through a gateway, wallets and bank transfer, then reconciles once a week against a spreadsheet. Integration marks invoices paid as confirmations arrive, sends unmatched credits to a review list for the accounts team, and stops reminders for customers who have already paid.
Retail Chain With One Price List
A retail chain runs the same billing software separately at each showroom, with rate changes typed in at every counter. Daily sales reach head office as an emailed backup file. Integration pushes the approved item, rate and offer master to each branch and pulls the day’s bills into central stock and accounts.
Is This Service Right for Your Business?
We partner with established businesses that have outgrown manual processes and want reliable systems.
Businesses Running Accounting Software Alongside Other Systems
Companies whose operations run in a portal, an app or a CRM while accounting sits in QuickBooks, Xero or Zoho Books. Someone bridges the two by hand today, usually with a spreadsheet, a daily export and a lot of patience.
Companies Selling Through Several Channels
Distributors, retailers and brands that take orders from a website, marketplaces, dealer portals and WhatsApp, and reconcile each channel separately at present, usually in its own spreadsheet. Totals rarely agree.
Multi-Branch and Multi-Plant Operations
Businesses with a separate copy of the software at each location. They need the same masters at every counter and each branch’s transactions reaching head office, without moving every site onto a new system at once.
Teams With an Unreliable Existing Integration
Organisations with an earlier connector that drops records silently, cannot be monitored, or breaks whenever a vendor updates an API. Repair is often cheaper than rebuilding.
Companies Adding a New System to an Existing Stack
Businesses introducing a customer portal, field app, payment gateway or logistics partner, where the new system has to exchange data with software that is already in daily use. Day one matters.
When Integration Is Not the Right Answer
With a single system, or a handful of records a week, a scheduled export or a shared sheet is simpler to maintain. Where the source data is unreliable, integration only spreads the errors, so data entry gets corrected first. We say so during discovery.
Enterprise Capabilities in Plain Business Terms
Field-Level Data Mapping
A written map of every field covers its format, its default and its meaning in both systems, and it is signed off before the build starts.
Master System Rules
Each data element has a defined owner, so a conflict has a decided outcome and the last write never wins by accident.
Real-Time and Scheduled Sync
Event-driven flows suit payments, order status and enquiries, while batch windows suit price lists, stock and ledger balances that change less often. The mode is chosen record type by record type.
Automatic Retries
Failed calls are retried on a spaced-out schedule, so short outages and rate limits recover without manual action. Nobody is paged for a blip.
Duplicate Protection
Every message carries a unique reference key, so a retry or a replayed webhook cannot create a second invoice or lead. Duplicates are refused.
Failed-Message Queue
Anything undeliverable is held with its payload and error message, then corrected and reprocessed once the cause is fixed. Nothing is lost meanwhile.
Reconciliation Reports
Daily counts and value totals are compared across both systems, and differences are listed line by line for the accounts team to clear. Gaps show up the next morning.
Failure Alerts to People
Notifications go to email, WhatsApp or a dashboard when a sync stops, a token expires or an error threshold is crossed. A person always hears first.
Complete Message Logs
A searchable history records what was sent, when, by which process and with what response. Logs are kept for the retention period the client specifies, and older entries are purged on schedule.
Secure Credential Handling
API keys and tokens are stored encrypted outside the code and scoped to minimum permissions, and they can be rotated without a redeployment. A leaked key stays short-lived.
Rate Limit and Quota Handling
Call pacing and queuing follow each vendor’s published limits, which protects the account from throttling or suspension when a bulk price update runs. Bursts are spread out.
Staging Environment Testing
Integrations are tested against sandbox or test accounts using the client’s real record shapes, and live data stays untouched until testing is complete. Production waits.
Our Structured 6-Step Delivery Process
A transparent path from your first conversation to a reliable production release.
- 01
Discovery and System Audit
The people who currently move the data are consulted, and every system involved is listed with what it holds and where double entry happens. The client provides read access or sample exports from both sides, and one contact per system answers our questions.
- 02
Integration Blueprint and Field Mapping
The mapping document covers records in scope, direction of flow, field-by-field translation, master rules, sync frequency and behaviour on conflict or failure. Build starts only after the client signs it off.
- 03
Access, Authentication and Environment Setup
This step defines how each system will be reached and with what permissions. The client raises API credentials in its own name with the vendors, provides sandbox accounts where they exist, and approves network access for on-premise systems. Keys never travel by email.
- 04
Connector and Middleware Build
APIs, transformation logic, queues and scheduling are built together with retries, duplicate protection, logging and alerting, never bolted on afterwards. Progress is shown against the mapping document. Finished flows are visible at each stage.
- 05
Testing, Reconciliation and Go-Live
The integration runs first on test data and then in parallel with the current manual method, and both sides are reconciled until the totals match. The client nominates the users who confirm results, and an acceptance point is agreed before the manual process is switched off. Both sides sign.
- 06
Monitoring, Handover and Support
You receive the code, the field mapping, the API notes and a runbook, and whoever will monitor the sync dashboard is walked through it. Support can then cover vendor API changes, credential renewals and new flows.
What You Receive Upon Project Completion
Everything required to run, maintain, and expand your software without vendor lock-in.
Connects With the Systems You Already Rely On
We build bridges between your software so you don't have to replace functional existing tools.
Accounting and ERP
- Xero
- Zoho Books
- Odoo
- QuickBooks
- Custom and legacy ERPs
CRM and Sales
- Zoho CRM
- Salesforce
- HubSpot
- Custom CRM databases
Payments and Collections
- Stripe
- PayPal
- Adyen
- Wallet and bank-transfer collections
- Bank statement and settlement files
Messaging, Commerce and Logistics
- WhatsApp Business API
- Transactional SMS providers
- Transactional email services
- Shopify
- WooCommerce
- Marketplace seller panels
- Courier and shipping APIs
Workspace and Utilities
- Google Workspace
- Microsoft 365
- Google Maps
- E-signature services
- SFTP and file exchange
Selected for Reliability, Speed, and Longevity
Technology chosen to match your operational scale and long-term maintainability.
APIs and Services
Integration and Messaging
Data and Storage
API Documentation and Testing
Deployment and Monitoring
Why Business Owners Choose GullySystem
Sample Data Is Read Before Quoting
Sample records show more than a requirement list. Inconsistent item codes, duplicate customers and free-text fields cause most of the trouble, and finding them early keeps the scope realistic. Surprises cost less before quoting.
Failure Handling Is Part of the Build
Retries, duplicate keys, dead-letter queues and alerts are built alongside the normal flow and shipped in the first release. They are never sold later as an upgrade.
No Rip and Replace
If the accounting, billing or branch software works, it stays and the connection is built around it. Where a system cannot support the requirement, we say so plainly and name the limit it hits.
Written Contracts Between Systems
The mapping sheet and API documentation are delivered, so another developer or vendor can work with the integration without reverse-engineering it. Nobody is locked in.
Credentials Stay in the Client’s Name
Gateway, WhatsApp, marketplace and cloud accounts are created under the client’s business, and GullySystem access is scoped and can be revoked. The client never depends on us for keys. Nothing is held back.
Support for Later API Changes
Third-party APIs deprecate endpoints and rotate credentials on their own schedule, and support arrangements exist because an integration needs attention after go-live as well as before it. Vendors change things without asking.
Flexible Engagement Options
Choose an engagement model that matches your operational scope, budget, and timeline.
Fixed-Scope Integration
Suited to a bounded requirement such as orders into accounts or leads into a CRM, with cost confirmed against an agreed mapping document and acceptance criteria. Scope stays fixed.
Phased Connector Rollout
The first connection is the one that removes the most manual effort, so it goes into production alone. The next flow follows once the team is comfortable.
Integration Audit and Repair
An existing integration is reviewed. What it actually does gets written down. Logging, retries and alerting are added where they are missing, and whether any part needs a rebuild is decided afterwards.
Managed Integration Support
Suited to businesses with several live connections. It covers watching the sync dashboard, renewing credentials before they expire, adjusting for vendor API changes and adding new flows as systems grow.
Frequently Asked Questions
Straightforward answers to the questions owners ask before getting started.
Are API integration services only worth it for large companies?
No. Volume and effort decide it, not company size. Where a team retypes the same records every day, or two systems keep disagreeing about the same customer, integration is a reasonable fit. With one system and a handful of records a week, a scheduled export is simpler. Discovery says so plainly.
Can you integrate with accounting software that has no API?
Yes. An API is the cleanest route. It is not the only one. Where a system has none, the options include database views, ODBC, scheduled file exchange over SFTP and the system’s own import and export formats. A small agent installed alongside it is another route. Discovery confirms which one each system supports.
Can you integrate old on-premise or legacy software?
Yes, in most cases. Legacy applications usually expose data through their database, a reporting view or scheduled exports, and that is enough for a one-way or two-way flow. It needs read access, permission from whoever supports the software, and clarity on which records may be written back. If the vendor blocks all access, we say so instead of working around it.
Can card payments and WhatsApp enquiries sync in real time, or does it have to run on a schedule?
It depends on the record type. Payments, order status and enquiries are usually event-driven. Master data such as item lists, price lists and ledger balances often suits scheduled batches, which are gentler on vendor rate limits. The mode is decided record by record during mapping.
What happens when a sync fails?
It is caught, retried and reported. Each message carries a unique reference, so a retry cannot create a duplicate, and failed calls are retried on a spaced-out schedule. Anything still failing is held in a queue with its data and error message, and an alert goes to a named person who can correct and reprocess the record. Daily reconciliation counts show whether anything was dropped.
How do you protect our data while it moves between systems?
Data moves over encrypted connections, with credentials stored outside the code and scoped to the minimum permissions each system needs. On-premise connections use a controlled route. No open server is involved. Log access is restricted and sensitive fields can be masked. An NDA can be signed before discovery.
What drives the cost of an integration project?
It depends on the scope of the flows and the state of the data, not a flat per-system fee. The main factors are how many record types move and in which directions, whether each system has a usable API, and how consistent the existing data is. Transformation effort, historical records and the level of monitoring also count toward the price. Each flow is priced separately after discovery, so some can be committed now and others deferred until the first is stable.
What decides how long the work takes?
Access and data quality matter more than writing the connector. The main inputs are how quickly each vendor issues credentials and sandbox accounts, how consistent the existing records are, and how many exceptions the mapping uncovers. A change needed on a third-party vendor’s side also counts. So does the parallel run. Discovery turns these into a dated schedule.
Do we need to move historical data as well?
Usually not all of it. Most businesses need only open items to move across, such as unsettled invoices, active customers, live orders and current stock. Full history is worth migrating only for reporting continuity or an audit trail in the destination system. Where it is required, the data is cleaned, de-duplicated and trial-loaded, and totals are reconciled against the source before the live load.
Do we own the source code, documentation and credentials?
Yes, all three. The client receives the complete source code with repository access, the field mapping sheet, the API documentation and the runbook. Vendor accounts and API credentials are created in the client’s business name. GullySystem access is scoped and revocable. Nothing is licensed back.
Will you train our team and support the integration after go-live?
Yes. The people who will use the sync dashboard and handle exceptions are trained in plain language. A short runbook explains what each alert means and what to do about it. A support arrangement after go-live can cover monitoring, failure investigation, credential renewals, vendor API changes and additional flows.
What do you need from us to get started?
Four things. First, a named contact for each system who can explain how it is used. Second, read access or sample exports from both sides. Third, permission to raise API credentials and sandbox accounts with the vendors in the client’s name. Last, one operations person who can settle business rules when two systems disagree. That role matters most. Integration decisions are business decisions first.
Why not just connect our systems with Zapier or Make instead of building a custom integration?
Zapier or Make is a sensible start for two standard apps at low volume. A custom integration becomes relevant when per-task pricing grows into a real monthly cost, or when the logic depends on conditions such as customer group, branch or credit limit. It also fits when a delay of a few minutes causes a stock mismatch. Many businesses run both, with simple flows on a no-code tool and critical flows built as code.
Read before you decide.
Practical notes on the questions this service raises, not product marketing.
What Is an API Integration?
What an API integration actually is, how it works, and when a small business needs one: explained through an everyday order example.
Signs That Your Business Systems Need Integration
Concrete signs that disconnected software is costing you money, and how to tell a genuine integration gap from a process problem.
How System Integration Eliminates Duplicate Data Entry
How connecting two business systems removes repeat data entry: source-of-truth rules, ID mapping, and what still needs a human check.
How to Integrate CRM, ERP and Accounting Software
A practical plan for connecting CRM, ERP and accounting software: data ownership, shared IDs, reconciliation, and a phased rollout.
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Share your requirementsRelated Practices & Services
Business Process Automation
Once your systems exchange data, automate the approvals, alerts and follow-ups that run on top of it.
ERP and CRM Implementation
Implementation and configuration when the answer is a properly set-up ERP or CRM rather than another connector.
Data Engineering and Business Intelligence
Turn the consolidated data your integrations produce into reliable reporting and management dashboards.
Custom Software and Product Engineering
Build the portal, app or platform that sits at the centre of your connected systems.