Custom POS Software Development in India

Description

Service Custom POS software development: billing, stock and GST built around your counter

A custom POS is billing software built around how your counter works: your price rules, your stock, your GST invoice format and the hardware already on the desk. WavX builds POS systems for retailers whose billing a ready-made app cannot handle. For a single shop with standard billing, a ready-made app is cheaper and this page says so.

Tell us what you need built Last updated 2 October 2026

When a custom POS is the right call

A point-of-sale system does three jobs: it produces a legal bill quickly, it keeps stock correct as items sell, and it tells the owner what happened today. Ready-made billing apps do all three for a standard shop. A custom build earns its cost only when one of the three has a rule the ready-made product cannot follow.

Your situation

Better choice

Why

One shop, barcode items, standard GST billing

Ready-made billing app

Works on day one; the monthly fee is small next to a build

Pricing the app cannot express: weight plus making charge, customer-wise rates, scheme and slab discounts

Custom

Staff stop working around the software with a calculator

Several counters or stores, and a per-counter fee that keeps rising

Compare the totals

Add up both over three years, not one month

Billing must update another system you already run: an ERP, a warehouse, an online store

Custom, or an integration

One stock figure instead of two that disagree

The counter cannot stop when the internet drops

Custom, designed offline-first

Offline billing has to be planned from the start

You want one system for billing, purchase and accounts and have no unusual rules

Ready-made accounting suite

It already does this

The longer comparison, with what ready-made products do well, is in POS software for retail in India: custom vs ready-made .

What WavX builds into a POS

WavX builds a POS as a web application with a fast billing screen, in React and Node.js with PostgreSQL. The modules below are the usual set; a first version rarely needs all of them.

Module

What it does

Decide before the build

Billing counter

Scan or search, quantity, discount, tax, hold and recall a bill, print or send it

Keyboard-only billing or touch; how many clicks a common bill takes

Catalogue and pricing

Items, variants, units, barcodes, HSN codes, price lists, schemes

Who may change a price, and whether it varies by store or customer

Stock

Reduces stock on sale, adds on purchase, transfers between stores, stock count

Batch and expiry, serial numbers, or simple quantity

Purchases

Supplier bills, purchase returns, landed cost

Whether purchase entry happens in the POS or in accounts

Payments

Cash, UPI, card and credit sales, split payment, day-end cash count

Whether the payment terminal reports back or the cashier confirms

Returns and exchanges

Credit notes against the original bill

Refund rules and who approves them

Customers

Phone-number lookup, purchase history, credit ledger

Whether loyalty points are needed at the counter

Users and roles

Cashier, supervisor, owner; an audit log of edits and voids

What a cashier must never be able to do alone

Reports

Day book, sales by item and store, tax summary, margin

The five reports the owner reads every day

Accounting export

Sales and tax data for the accountant or for Tally

Push each bill, or a daily summary

Stock is the module that grows fastest. If stock control is the real problem, read the inventory management software page first; the POS may be the smaller half of the project.

GST on the bill: what the software has to get right

In India a POS is a GST invoicing system before it is anything else. The points below are summarised from the sources listed on this page, read on 2 October 2026. They describe what the software must be able to do; how the rules apply to your business is your accountant's call.

Rule

What it means for the software

Invoice contents. Rule 46 of the CGST Rules lists what a tax invoice carries: the supplier's name, address and GSTIN, a serial number, the date, a description, the HSN code, quantity, taxable value after discount, and the rate and amount of each tax.

The stored bill and the print layout hold every field, on thermal paper as well as A4.

Serial numbers. The number must be consecutive, at most sixteen characters, unique for the financial year, in one or more series.

Each counter gets its own series so two tills can never issue the same number, including when they bill offline.

Buyer details. For an unregistered buyer, name, address and state are required once the taxable value is ₹50,000 or more.

The billing screen asks for them at that value, and takes a GSTIN when a business customer wants a tax invoice.

Small bills. An invoice need not be issued for a supply under ₹200 to an unregistered buyer who does not ask for one, subject to conditions; a consolidated invoice is then issued at the close of each day.

If you use this relaxation, the day-end routine creates the consolidated invoice.

HSN digits. Notification 78/2020-Central Tax ties the minimum number of HSN digits to turnover: four up to ₹5 crore of aggregate annual turnover, six above it.

The catalogue stores the full code for each item and the print format shows the digits you are required to show.

Bill of supply. A composition dealer, or a seller of only exempt goods, issues a bill of supply instead of a tax invoice.

A registration setting changes the document type and removes the tax columns.

Rates change. The 56th GST Council meeting recommended replacing the four-rate structure with 5% and 18% rates and a special 40% rate, effective 22 September 2025 for most goods and for services.

Rates are data with an effective date, not code. An old bill reprints with the rate that applied on its date.

E-invoicing. Notification 10/2023-Central Tax applied e-invoicing to taxpayers with aggregate turnover above ₹5 crore from 1 August 2023. It covers invoices to registered buyers and exports.

The POS needs a link to the invoice registration portal only if you are above the notified threshold and bill registered businesses. See GST e-invoicing integration .

Thresholds and rates are set by notification and do change. A custom POS should keep every one of them in a settings screen that your accountant can read.

Hardware: what the software has to talk to

No brand is assumed here. The exact model numbers on your counter are tested before a quote is fixed, because this is where POS projects lose time.

Device

How software reaches it

What to check

Thermal receipt printer

Through the operating system's print driver, or by sending the printer's own command set. Epson's ESC/POS is one such command system, which Epson describes as proprietary; other makers use their own or a compatible one. Printers connect by USB, serial or Ethernet depending on the model.

Paper width, whether the printer has the fonts for your bill language, and how fast one bill prints

Barcode scanner

Most USB scanners can be set to behave as a keyboard, typing the code into whichever field has focus.

That the billing screen always returns focus to the scan field

Barcode label printer

A separate printer with its own command language and label sizes.

Label size, and whether weight or price is encoded in the barcode

Cash drawer

On many receipt printers the drawer plugs into a drawer-kick connector on the printer, which opens it. Epson documents this connector for its TM-T20IIIL.

That your drawer and printer are compatible

Weighing scale

Model-specific; some send the weight over a serial connection.

Whether the scale has a documented output at all

Card or UPI terminal

Depends on the payment provider. Some offer an integration; with others the cashier confirms the payment by hand.

What your provider supports before promising automatic reconciliation

One browser limit matters. A web page cannot reach a USB printer directly in every browser: MDN lists both WebUSB and the Web Serial API as limited-availability features that do not work in some widely used browsers. A browser-based POS therefore prints through the system print dialog, through a network printer, or through a small local print service installed on the counter machine. Which one is decided in the first week, with your hardware.

Offline billing

If the counter must keep working without internet, three things are designed in from the start:

Local storage. The catalogue, prices and open bills live on the counter device.

Invoice numbers. Each device issues from its own series, so numbers stay consecutive and unique without asking a server.

Sync rules. When the connection returns, bills upload in order. Stock can go below zero while offline, and the system reports it instead of blocking the sale.

Offline-first costs more to build and to test. If your connection is reliable and a few minutes of downtime is acceptable, an online POS with a mobile-data fallback is simpler.

Planning range

These figures come from the WavX cost model, the same one behind the software cost estimator . The range is the subtotal less 15% to the subtotal plus 25%. It is a planning range, not a quote.

Scenario

Cost model inputs

Subtotal

Timeline band

Single-store counter billing

Internal tool base ₹2,00,000; roles ₹60,000; exports and reporting ₹50,000

₹3,10,000

₹2,63,500 to ₹3,87,500

6–10 weeks

Multi-counter POS with stock and payments

Custom web application base ₹4,50,000; roles ₹60,000; payments and billing ₹90,000; admin panel ₹90,000; exports and reporting ₹50,000; third-party integrations ₹60,000

₹8,00,000

₹6,80,000 to ₹10,00,000

10–16 weeks

Assumptions: small scale (multiplier 1.0), standard interface design, hardware bought separately, and offline-first billing not included. A custom interface design multiplies the subtotal by 1.25 in the estimator. Yearly maintenance is 15–25% of the build cost, as set out in the maintenance cost guide .

How the build runs

Counter study. WavX watches or records how bills are made today, lists every price and discount rule, and collects the hardware model numbers.

Tax and catalogue setup. Item list, HSN codes, rates and invoice series are agreed with your accountant and imported.

Billing first. The billing screen and print are built and shown before anything else, because cashier speed decides whether the project succeeds.

Stock, purchases and reports. Added once billing is right.

Hardware test. On your printers and scanners, with your paper.

One-counter pilot. The new POS runs beside the old one for a few days, and the day-end totals are compared.

Roll-out and training. Counter by counter, then store by store.

The source code and the data belong to you at the end. The owner-level walkthrough of the same steps is in how to build a POS system for retail .

What to ask any POS developer

Which invoice fields are stored, and can you show a sample bill for a registered and an unregistered buyer?

What happens to invoice numbering with two counters, and when the internet is down?

Where are tax rates kept, and who can change them?

Which printer and scanner models has the quote been tested against?

What does the day-end report show, and does it match the cash in the drawer?

Who owns the code and the database, and how is a backup restored?

POS development is one part of custom software and business systems at WavX. For a retailer who wants billing, stock and accounts described together, start with retail billing software.

Frequently asked questions

Is a custom POS worth it for a single shop?

Usually not. If your billing is standard, with barcode items, GST and a few payment modes, a ready-made billing app costs far less and works on day one. Custom becomes worth it when the software cannot follow a rule your business depends on, or when per-counter fees across many counters and stores cost more than owning the system.

Will the POS keep billing when the internet is down?

It can, if it is designed for it from the start. The counter stores bills locally, issues invoice numbers from its own series and syncs when the connection returns. Adding offline billing to a POS that was built online-only is a large change, so say it is needed before the build begins.

Which printers and scanners will it work with?

That is settled in the first week by testing the actual models on your counter. Most USB barcode scanners can act as a keyboard and need no integration. Receipt printers differ by command set and by connection, so we ask for the exact model numbers before quoting.

Does the POS file my GST returns?

No. It produces correct invoices and the sales, tax and HSN summaries your accountant or accounting software needs. Return filing stays with your accountant. If e-invoicing applies to you, the POS can be integrated with the invoice registration portal through a GST Suvidha Provider.

How much does a custom POS cost?

The WavX cost model gives a planning range of about ₹2.6 lakh to ₹3.9 lakh for single-store counter billing and ₹6.8 lakh to ₹10 lakh for a multi-counter POS with stock, payments and integrations. These are planning ranges, not quotes. The software cost estimator shows how each feature changes the figure.

Sources

CBIC: Rule 46 of the CGST Rules, 2017 (tax invoice) · read 2 October 2026

GST Council: Tax invoice and other such instruments in GST (flyer) · read 2 October 2026

GST portal advisory on HSN codes (Notification 78/2020-Central Tax) · read 2 October 2026

PIB: Recommendations of the 56th meeting of the GST Council, 3 September 2025 · read 2 October 2026

GST Council: Notification 10/2023-Central Tax (e-invoicing above ₹5 crore from 1 August 2023) · read 2 October 2026

GSTN: GST e-invoice system FAQs, version 1.3 dated 11 November 2020 · read 2 October 2026

Epson: TM-T20IIIL Technical Reference Guide (ESC/POS command system, connectors) · read 2 October 2026

MDN: WebUSB API · read 2 October 2026

MDN: Web Serial API · read 2 October 2026

Related

Inventory management software

POS software for retail in India: custom vs ready-made

GST e-invoicing integration

Software cost estimator

Custom software and business systems

Build your own software — your way, your pricing.

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