Custom web application development
React, Next.js and Node.js applications with role-based access, real-time dashboards, document workflows and the integrations a UK business runs on, built for scale from the first release.
Software Development · London (Dagenham)
Software Development Company in London
Custom web applications, mobile apps, business systems and AI features engineered for London companies, with UK data protection, Making Tax Digital and the integrations a UK business runs on designed in from the first sprint.
Off-the-shelf software rarely fits a London business for long. The professional services firm outgrows its practice management tool, the property agency runs four systems that do not talk to each other, the clinic group manages bookings in one place and records in another, and the distributor has a warehouse system that does not know what the website sold.
Infynix Solutions builds the systems that replace that patchwork. Web applications, mobile apps, ERP and CRM platforms, integrations and AI-assisted features, delivered through a process that starts with how the business actually operates rather than a feature list. Our UK company works from Dagenham, with engineering capacity from our teams in the UAE and India, and London client work happens on site as often as it needs to.
The systems we build in the UK carry requirements a generic vendor will not think about until it is expensive: UK GDPR and the data subject rights it creates, Making Tax Digital for VAT and, from April 2026, for income tax, HMRC-compatible records, Open Banking and the UK payment landscape, accessibility to WCAG, and the integrations with Xero, Sage, QuickBooks and the tools a UK business already runs.
We work with professional services firms, property and lettings businesses, clinics and healthcare groups, logistics and distribution companies, e-commerce brands, hospitality groups and startups. Some need one focused application. Most need the connective tissue between the systems they already have.
How we work
- 01
Discover
A paid discovery phase producing a scoped roadmap you own outright.
- 02
Architect
Data model, integrations and infrastructure agreed before code.
- 03
Build
Fortnightly demos, working software, no black box.
- 04
Hand over
Your repositories, your infrastructure, documented.
Software development services for London
Mobile app development for iOS and Android
Native and cross-platform apps in React Native and Flutter, with App Store and Google Play compliance, UK payment integration and privacy handled as part of delivery.
Business systems and ERP
Odoo implementation and customisation, or bespoke modules for inventory, sales, operations, HR and finance, configured for UK VAT, Making Tax Digital and HMRC records.
CRM development and integration
HubSpot, Zoho, Salesforce and Pipedrive implementation, or custom CRM builds for sales processes with UK GDPR consent and data subject rights handled.
E-commerce platforms
Shopify Plus, WooCommerce and headless builds with Stripe, Adyen, GoCardless, Klarna and Clearpay integration, Royal Mail and DPD connections and returns handled properly.
System integration and APIs
Connecting ERP, CRM, accounting, e-commerce, banking and HMRC so data is entered once and flows everywhere it is needed.
AI features and automation
Document extraction, forecasting, assistants trained on your own data and workflow automation that removes the manual steps between systems.
Cloud infrastructure and DevOps
AWS, Azure and Google Cloud deployments in UK regions, with CI/CD pipelines, monitoring, backups and security hardening.
What a London build includes by default
UK GDPR by design
Consent, purpose, access, portability and erasure handled in the product, with records that satisfy the ICO.
Making Tax Digital readiness
Digital records and API links for VAT, and for income tax as the mandate phases in from April 2026.
Accounting integration
Xero, Sage, QuickBooks or FreeAgent fed automatically so the finance team keeps the tool they know.
UK payments
Stripe, Adyen, GoCardless, Open Banking, Klarna and Clearpay integrated as the business needs, with reconciliation built in.
Accessibility
WCAG-aligned interfaces, which public sector and regulated buyers increasingly require of their suppliers.
UK hosting
AWS London, Azure UK South and Google Cloud London, with backups kept in region.
Security practice
Role-based access, encrypted secrets, dependency scanning and penetration testing where the risk justifies it, with Cyber Essentials in mind.
Full handover
Source code, infrastructure, documentation and credentials in your name. You are never locked to us.
Typical scope and timeline
| Engagement | Typical timeline |
|---|---|
| Discovery and technical specification | 2 to 3 weeks |
| Focused web tool or integration | 4 to 8 weeks |
| MVP web or mobile application | 8 to 12 weeks |
| Odoo or business system implementation | 10 to 20 weeks |
| CRM implementation and integration | 4 to 10 weeks |
| Enterprise platform | 4 to 8 months |
| Support and maintenance | Monthly |
Systems we build most often in London
Professional services
Client portals, matter and case management, time and billing, document workflows and the compliance records a regulated firm keeps.
Property and lettings
Property, tenant, maintenance and compliance systems with portal integration and the certificates a landlord must hold.
Clinics and healthcare
Patient management, scheduling, records and reporting across sites, with health data obligations respected.
Logistics and distribution
Inventory, dispatch, tracking, proof of delivery and customer portals connected to billing.
E-commerce and retail
Storefronts, order management, returns and marketplace integration with Amazon UK and eBay where the channel justifies it.
Startups and scale-ups
Product builds for companies that need a senior team without hiring one, with architecture documented for the in-house team that follows.
How we engage
Fixed-scope project
Discovery produces a specification and a fixed price. Best when the problem is well understood and the scope can be agreed before code is written.
Dedicated team
A named team working on your roadmap month to month, with sprint planning and demos. Best for products that keep evolving.
Discovery first
A paid two to three week engagement that produces the specification, architecture and estimate, whether or not we build it.
Support and evolution
SLA-backed maintenance, monitoring and continuous improvement for systems we built or inherited.
Building for UK GDPR from the first sprint
UK GDPR is not a policy document. It is a set of behaviours a system must be able to perform: capture consent for a purpose, record the lawful basis, answer a subject access request within a month, correct and erase data on request, port it in a usable format, retain it only as long as needed, and report a breach within 72 hours. A system that cannot do those things from the interface forces the business to do them by hand, at exactly the moment a complaint or an ICO enquiry arrives.
We design consent, purpose limitation, retention and data subject rights into the product from discovery, host in UK regions, and document the data map so a compliance review finds the reasoning rather than a gap.
Consent and lawful basis
Captured and recorded in the product, per purpose, not bolted on as a banner.
Subject rights workflows
Access, correction, erasure and portability handled from the system within the statutory timeframes.
Retention
Data kept as long as needed and no longer, with rules the business can see.
Data map and records
Documentation that satisfies the ICO and any due diligence a client runs on you.
Making Tax Digital and HMRC-compatible records
Making Tax Digital for VAT has applied to all VAT-registered businesses since April 2022, requiring digital records and returns submitted through compatible software. From April 2026 it extends to income tax for sole traders and landlords above the income threshold, with quarterly updates through software. A system that touches sales, purchases or rental income needs to keep records in a form the mandate accepts and connect to the software that files.
We design the data model for digital records from the start, integrate with Xero, Sage, QuickBooks or FreeAgent so filing happens in the tool the accountant uses, and keep the audit trail HMRC can ask for.
Digital records
Transactions held in the form Making Tax Digital requires, with the digital links preserved.
VAT handling
Standard, reduced, zero-rated and exempt supplies handled correctly, with reverse charge where it applies.
Accounting integration
Xero, Sage, QuickBooks or FreeAgent fed automatically for filing.
Audit trail
The history HMRC can ask for, kept without effort.
Payments, delivery and the UK customer
UK commerce runs on card and Open Banking, on buy now pay later through Klarna and Clearpay, on Direct Debit through GoCardless for subscriptions, and on a delivery network of Royal Mail, DPD, Evri and DHL whose APIs vary widely in quality. Returns under the Consumer Rights Act and distance selling rules have to be handled properly, and customers expect tracking and updates by email and SMS.
We have integrated all of these and know where the edges are. The order system we build reconciles gateway settlements and refunds into the accounts, handles returns and refunds to the rules, and connects to the carrier network with tracking that reaches the customer.
Gateway integration
Stripe, Adyen, Checkout.com and Open Banking with 3D Secure and tokenisation handled correctly.
Subscriptions and Direct Debit
GoCardless and Stripe Billing for recurring revenue, with dunning and reconciliation.
Buy now, pay later
Klarna and Clearpay at checkout with settlement reconciled.
Carrier connections
Royal Mail, DPD, Evri and DHL integrated with tracking pushed to the customer.
Replacing legacy systems without stopping the business
Most London engagements are not greenfield. There is an accounting package that must stay, a legacy system that holds fifteen years of records, a practice management tool the partners will not give up, and a set of spreadsheets everyone depends on and nobody trusts. The job is to replace what is failing while keeping the business running, and to migrate data without losing history.
We plan migration as its own workstream: mapping, cleaning, trial migrations, reconciliation reports and a cutover plan with a way back. Legacy systems are wrapped with APIs and retired in stages rather than switched off on a Friday. The staff who run the old process are part of designing the new one, because they know where the exceptions are.
Data migration
Mapping, cleaning, repeated trial migrations and reconciliation so the new system opens with correct balances and history.
Staged retirement
Legacy modules replaced one at a time with both systems reconciled during the overlap.
Integration over replacement
Systems that work are integrated, not rebuilt. The accounting package usually stays.
Training and adoption
Role-based training and documentation, with the first month live supported closely.
AI features that earn their place
AI in a business system is worth building when it removes real manual work or makes a decision better, not because a pitch needed the word. In London businesses the practical wins are usually document handling and triage: extracting data from invoices, contracts and forms, classifying and routing enquiries, drafting responses to routine questions from your own documents, forecasting demand and cash flow, and flagging the exceptions in a process so a person only looks at the cases that need one.
We build these on top of the operational system, using your data, with humans reviewing output until the accuracy justifies removing them. Where the feature needs a language model, we choose the model and the hosting with UK GDPR in mind, and we document what data goes where.
Document extraction
Invoices, contracts, IDs and forms read into structured records with review queues for exceptions.
Triage and routing
Enquiries classified and routed to the right person with the context attached.
Assistants on your data
Internal and customer-facing assistants that answer from your documents and systems.
Forecasting and automation
Demand, cash and staffing forecasts, and approvals and hand-offs automated with exceptions routed to people.
How a build runs, week by week
Discovery takes the first two to three weeks: workshops with the people who run the process today, a map of the systems and data involved, a written specification, an architecture and a fixed estimate. Design follows, with clickable prototypes reviewed by the people who will use the screens, because the fee earner and the operations manager find the problems a project sponsor never sees.
Build runs in two-week sprints with a working demo at the end of each. Data migration rehearsals start early. User acceptance testing runs on a staging environment with real data. Go-live is planned with a cutover checklist, a rollback path and the team on site for the first days of live use. Support begins the day the system goes live.
Weeks 1 to 3
Discovery, specification, architecture and fixed estimate.
Weeks 3 to 5
Prototypes reviewed with the people who will use the system.
Sprints
Two-week cycles with a working demo at the end of each.
Go-live and support
Rehearsed cutover, on-site presence and SLA support from day one.
Security, hosting and support
A business system is only as good as its uptime and its security, and London clients increasingly ask their suppliers for evidence of both. We deploy to AWS, Azure or Google Cloud in UK regions, with infrastructure defined as code, automated backups tested by restoring them, monitoring that pages a person, and security practice covering access control, secrets management, dependency updates and penetration testing where the risk justifies it, aligned with Cyber Essentials.
After launch, support runs on a service level agreement with named response times, a monthly maintenance allowance and a roadmap for improvements. Systems inherited from other vendors go through an assessment first so we know what we are taking on.
Infrastructure as code
Environments reproducible from source, so recovery and scaling are procedures rather than emergencies.
Backups and recovery
Automated backups with tested restores and a documented recovery time.
Security practice
Role-based access, encrypted secrets, dependency scanning and periodic penetration testing.
SLA-backed support
Named response and resolution times, monitoring and a monthly improvement allowance.
Why a London partner with a three-market engineering bench
London engineering rates make senior teams expensive for a mid-sized business, and fully offshore vendors make discovery, migration and go-live hard to do properly. We work from Dagenham with engineers who come to your premises for the parts of a project that need a person in the room, and we draw engineering capacity from our teams in the UAE and Kochi for the sprints in between. The result is a senior team at rates a London business can sustain, with someone accountable in the same time zone.
The regulatory context we build for, UK GDPR, Making Tax Digital, PECR, the CQC and the SRA, is the context our UK clients operate in daily, and it is designed into the system rather than discovered at audit time.
On site when it matters
Discovery, migration and go-live at your premises.
Sustainable rates
Senior engineers without central London day rates.
Same-time-zone accountability
A UK team responsible for the outcome.
Built for UK rules
GDPR, MTD, PECR and sector regulation designed in.
Working with your existing IT, accountant and vendors
A London business usually already has an accountant on Xero or Sage, an IT support company, a hosting provider and maybe an agency that built the website. We work with all of them rather than around them. The accounting package stays. The IT company keeps the network and the devices. The system we build is documented so any of them can understand where it fits.
Where an existing supplier built something that needs to be replaced, we assess it honestly, migrate from it carefully and say so plainly if it should be kept. The goal is a business with fewer moving parts, not a business with one more vendor.
The accountant's tool stays
Xero, Sage, QuickBooks or FreeAgent kept and fed automatically.
Existing suppliers
Worked with, documented for, not worked around.
Honest assessment
What to keep, what to replace, what to integrate, in writing.
Fewer moving parts
The measure of success is a simpler business, not a bigger stack.
Engineering for London from East London
Infynix Solutions works from 39 Becontree Avenue in Dagenham and delivers software for businesses across London. Discovery workshops, sprint reviews, migrations and go-live happen on site, and the sprints between run remotely with a working demo every two weeks. Engineering capacity comes from our teams in the UK, the UAE and Kochi in India, which is how a mid-sized London business gets senior engineers at rates that make sense.
The discovery call is free and technical. Bring the current systems, the spreadsheets and the pain, and we will tell you what we would build first and what we would leave alone.
Frequently Asked Questions
How much does custom software development cost in London?
Scope drives the number, so the honest answer comes after a short discovery rather than before it. What we commit to in advance is that the quote is fixed for the agreed scope, that there are no surprise extras, and that we tell you when a cheaper route would serve you better.
How long does a typical software project take?
A focused tool takes 4 to 8 weeks. An MVP takes 8 to 12 weeks. A business system implementation runs 10 to 20 weeks depending on scope and data migration. Enterprise platforms take 4 to 8 months, delivered in releases so value arrives before the final milestone.
Do you build systems that comply with UK GDPR?
Yes. Consent, lawful basis, retention and data subject rights workflows are designed into the product, hosting is in UK regions, and the data map is documented so a compliance review or a client due diligence finds the reasoning rather than a gap.
Can you build for Making Tax Digital?
Yes. Digital records with preserved digital links, correct VAT handling and integration with Xero, Sage, QuickBooks or FreeAgent for filing are part of the standard data model, with income tax readiness as the mandate phases in from April 2026.
Which payment providers do you integrate?
Stripe, Adyen, Checkout.com and Open Banking for cards and bank payments, GoCardless and Stripe Billing for Direct Debit and subscriptions, and Klarna and Clearpay for buy now pay later, with settlement and refunds reconciled into the accounts.
Do you implement Odoo?
Yes. Odoo with UK localisation is our default recommendation when a business needs standard modules and not a fully bespoke system. We implement, configure, customise and integrate it, and build bespoke modules where it does not fit.
Can you integrate with Xero, Sage or QuickBooks?
Yes. Most London builds keep the existing accounting package and feed it from the operational system so the finance team works in the tool they know.
Where will our data be hosted?
In UK regions on AWS, Microsoft Azure or Google Cloud, with backups kept in region. The decision is made in discovery and documented, with UK GDPR and any client requirements in mind.
Do you provide support after launch?
Yes. Support runs on a service level agreement with named response times, monitoring, backups and a monthly allowance for improvements. We also take over systems built by other vendors after an assessment.
Can you modernise a legacy system without stopping the business?
Yes. We wrap legacy systems with APIs, migrate data in rehearsed stages with reconciliation at each step, and retire old modules one at a time. The business keeps running through the overlap and there is always a way back at cutover.
Who owns the code?
You do. Source code, infrastructure, documentation and credentials are handed over in your name, and the system is built so another competent team could run it.
Do you work on site in London?
Yes. Discovery, sprint reviews, migrations and go-live happen at your premises, and the sprints between run remotely with demos every two weeks. Our office is in Dagenham, with engineering capacity from our UAE and India teams behind the London team.
Do you sign NDAs and work with our existing IT support?
Yes to both. NDAs are signed before discovery, and we work alongside in-house IT, your IT support company, the accountant and existing developers, documenting the system so any of them can understand where it fits.
How quickly can you start?
Discovery can usually begin within two weeks of agreement, and the first working release is typically live within eight to twelve weeks of discovery ending.
Do you build mobile apps as well as web systems?
Yes. Customer, field and workforce apps in React Native and Flutter are built on the same engineering practice, with the backend, admin panel and App Store and Google Play compliance included.
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Tell us what you are trying to grow and we will tell you honestly whether we are the right people for it.
39 Becontree Avenue, Dagenham, Greater London RM8 2UH+44 7436 670553 · office@infynixsolutions.co.uk