ERP vs custom software for a growing business
Buy an ERP for standard accounting, inventory and HR. Build custom software for the processes that make you different, and connect the two. How to split it.
For most growing businesses, the right answer is both: an ERP for the standard back-office jobs like accounting, inventory, purchasing and payroll, and custom software for the processes that make your business different, connected to the ERP so data flows both ways. Buying an ERP and forcing every unusual process into it leads to expensive customisation and unhappy staff. Building everything custom means reinventing accounting, which is rarely a good use of money.
The trick is drawing the line in the right place. Here's how.
What an ERP is good at
ERP (enterprise resource planning) systems like SAP Business One, Oracle NetSuite, Microsoft Dynamics, Odoo, Zoho and, for many Indian businesses, Tally combined with add-ons, cover the standard operations of a company:
Accounting, tax and financial reporting
Purchasing and supplier management
Inventory and warehouses
Sales orders and invoicing
Payroll and HR basics
Manufacturing planning, in some products
These processes follow rules that are similar across companies, and in the case of tax and accounting, rules set by law. Good ERPs have encoded those rules and keep them updated. Rebuilding that yourself is expensive and risky.
Where ERPs struggle
ERPs are built for the common case. They get painful when:
Your core process is unusual. Custom manufacturing with complex configurations, rental and subscription models, project-based work with unusual billing, or multi-party approvals.
Customers or partners need their own portal to place orders, track jobs or see documents.
Field staff need a simple mobile app, not a cut-down ERP screen.
Customisation piles up. Every upgrade breaks your customisations, and each one needs a specialist consultant.
Licence costs per user become large for staff who only need one or two screens.
The warning sign is a growing collection of spreadsheets and workarounds around the ERP. Those show exactly where it doesn't fit. Our post on signs your business has outgrown Excel covers the same pattern.
How to draw the line
List your main processes. For each, ask two questions:
Is this process standard in our industry, or is it part of how we compete?
Does an ERP handle it well without heavy customisation?
Then sort them:
Standard and handled well: keep it in the ERP.
Standard but handled poorly by your current ERP: consider a better ERP or a specialised product.
Part of how you compete: this is where custom software earns its cost.
Common custom pieces around an ERP include customer and dealer portals, quoting and configuration tools, field service apps, production floor apps, specialised scheduling, and analytics dashboards that combine ERP data with other sources.
Connecting custom software to your ERP
The connection is what makes the two work together. Done well, staff enter data once, and it appears where it's needed.
Options depend on your ERP:
Modern ERPs have APIs, so custom software can read and write orders, customers, stock and invoices directly.
Older or on-premise systems may need scheduled imports and exports, or a small connector service.
Tally, common in Indian businesses, can exchange data through its integration options, and the right approach depends on your version and setup.
Decide which system owns which data. For example, the ERP owns customers, products, prices and invoices, while the custom portal owns quotes and customer requests until they become orders. Clear ownership prevents two versions of the truth.
Plan for failure too. Integrations break when a password changes, an API version is retired or a network blips. A good connector retries, logs every failure, and alerts someone when an order didn't make it across, so problems surface in minutes instead of at month-end reconciliation. It's also worth deciding upfront what happens if the ERP is down for maintenance: the portal can queue orders and send them later, instead of turning customers away.
A worked example
A distributor of industrial parts runs accounting, stock and invoicing in its ERP. Its dealers used to order by phone and WhatsApp, and staff typed orders in by hand. A custom dealer portal lets dealers see their prices and stock, place orders, and track deliveries. Orders flow straight into the ERP as sales orders, and invoices flow back to the portal. The ERP stays as it was. The typing disappears.
Cost and timeline
ERP costs are licences or subscriptions, implementation, and customisation. Custom software costs a build plus maintenance. Our guide to custom software development cost covers the ranges.
A focused custom tool around an ERP, like a dealer portal or a field app with one integration, typically takes 8 to 16 weeks. Replacing a whole ERP with custom software is a much bigger decision, sensible only when your business model genuinely doesn't fit any ERP on the market.
Questions about ERP and custom software
Should a small business buy an ERP?
Once accounting, inventory and orders outgrow separate tools and spreadsheets, yes. Many affordable cloud ERPs suit small businesses. Start with the modules you need and add others later.
Can custom software replace an ERP?
It can, but it rarely makes sense. Accounting, tax and inventory rules are complex and keep changing. It's usually better to keep an ERP for those and build custom software for what makes you different.
Is customising an ERP better than building separate software?
Light configuration is fine. Heavy customisation often becomes expensive to maintain and can break with upgrades. For large, unusual processes, separate custom software connected by API is usually easier to live with.
How do custom apps connect to Tally or SAP?
Through the ERP's integration options: APIs, connectors, or scheduled data exchange. The best method depends on your ERP version and hosting, which is worth confirming early in the project.
Get help drawing the line
Walk us through your processes and your current ERP. We'll tell you what should stay in the ERP, where custom software would pay off, and give you a fixed price for the first piece.