Subscription Billing Development

I DEVELOP SUBSCRIPTION BILLING PLATFORMS THAT SHIP IN WEEKS, NOT QUARTERS

I'm Ajeet Kumar. I design, build and automate custom subscription billing platforms for SaaS founders and ecommerce technology leaders — reducing billing complexity, eliminating manual finance workflows, and getting a working slice into production before an in-house rebuild would even have finished planning.

Book a Discovery CallSee the development process
First shippable slice in 4–6 weeks
Billing automation replacing manual finance work
Documented, tested, hosted in your account

A Typical Delivery Timeline

  1. Week 1–2

    Discovery & written architecture

  2. Week 3–6

    First shippable billing slice in staging

  3. Week 7–10

    Provider integration + dunning + reconciliation

  4. Week 11+

    Shadow run, cohort migration, cutover

Timelines vary. Discovery is fixed-scope; delivery is phased and re-approved every phase.

Why Building It In-House Stalls

The Long Tail of Subscription Billing Is Where Roadmaps Die

In-house billing builds ship the easy 80% on time and then bleed engineers for months on the parts nobody scoped.

The 80/20 that isn't

A junior engineer ships 80% of the billing platform in a sprint. The remaining 20% — proration edges, tax rounding, webhook races, plan grandfathering — takes six months and quietly gets abandoned.

Coupled to product code

Billing logic lands inside product endpoints, so every pricing change becomes an application deploy and a regression risk. There is no seam to test.

Silent data drift

Your dashboard, your billing tool, and your bank all show slightly different MRR. Nobody knows which one is right, and nobody has time to build the reconciliation job that would tell them.

Engineering focus tax

Every billing incident pulls senior engineers off product work. The roadmap slips, the fix ships late, and the cycle repeats next month.

Development Capabilities

What I Develop for You

A focused set of subscription billing development capabilities. Every engagement mixes them differently — I don't sell packages, I build what your product actually needs.

Custom Subscription Billing Platform Development

Purpose-built subscription billing platforms with your pricing model as the source of truth — plans, add-ons, seats, metered usage, hybrid pricing — instead of contorting a hosted tool.

Billing Automation Engineering

Replace manual finance workflows with billing automation: invoice runs, dunning, credit notes, refunds, tax and revenue recognition — all triggered by data, not by a person opening a spreadsheet on Friday.

Recurring Billing Software Modernisation

Rewriting or refactoring legacy recurring billing software so it stops being the reason engineers dread a pricing change. Same features, cleaner core, tests you can trust.

Subscription Management Solutions

Self-serve upgrade/downgrade flows, admin overrides for CS, plan versioning, entitlement checks — the subscription management solutions your product needs but off-the-shelf tools bury behind their own UI.

Payment Gateway Integration

Payment gateway integration with Stripe, Authorize.Net, PayPal, Razorpay, PayU and other providers — global and Indian payment gateways — wired to a single internal interface so switching or adding a provider is a config change, not a rewrite.

API Integration Services

API integration services connecting your billing platform to HubSpot, accounting software, tax engines and data warehouses — same customer, same numbers, everywhere.

The Development Process

A Five-Stage Delivery Model

Every subscription billing platform I develop follows the same five stages. The scope changes; the discipline doesn't.

01

Discover

A short paid audit of your current billing setup: pricing plans, edge cases, provider quirks, data flows. You leave with a written map of what needs custom work and what doesn't.

02

Design

A concrete architecture for your subscription billing platform: schema, event model, provider adapters, retry and reconciliation rules, and the API your product will consume.

03

Build

Delivered in slices. Each slice is independently shippable — plan CRUD, checkout, dunning, invoicing, tax — so value appears in weeks, not quarters.

04

Launch

Shadow-run against your existing setup, migrate customers in cohorts, watch reconciliation reports match, then cut over. No mystery outages the day billing goes live.

05

Iterate

Post-launch optimisation: dunning tuning, retry windows, plan experiments, and a running list of small changes that quietly compound into recovered revenue.

How the Delivery Cuts Complexity

Four Levers I Pull On Every Engagement

Speed

Weeks to first working slice

First working billing slice — usually plan CRUD plus a single provider checkout — inside 4 to 6 weeks. Not a demo. Real code, in your account, that your team can build on.

Simplicity

A single billing seam in your product

Your product code stops touching Stripe, Authorize.Net, PayPal, Razorpay or PayU directly. It talks to one internal billing API. Adding a plan, a coupon or a provider stops being a cross-file refactor.

Reliability

Failure paths built in from day one

Idempotent event handling, signature-verified webhooks, retry queues, dead-letter handling, and a nightly reconciliation job — before the first customer is billed, not after the first incident.

Ownership

Documented, tested, yours

Every component ships with tests and a README aimed at your next engineer. If we part ways, your team keeps running. No vendor lock, no bus factor of one.

Engagement Models

Three Ways to Work Together

Start small. Every engagement begins with either an audit or a scoped first slice — you never sign up for a giant project on trust alone.

Billing Audit

Fixed scope

A 1–2 week paid audit of your subscription billing platform. Written findings, prioritised risks, and a scoped plan for what to build, buy, or leave alone.

  • Architecture review
  • Failure-path assessment
  • Written recommendations
Most Common

Build Engagement

Phased delivery

Fixed-scope, phased development of your subscription billing platform — first slice in weeks, each phase independently useful. You approve the next phase after seeing the last one working.

  • Phase-by-phase pricing
  • Working software each phase
  • You own the code

Ongoing Partner

Monthly retainer

A senior technical partner on call for pricing changes, new provider work, incident response, and the long-tail billing automation that keeps compounding after launch.

  • Capped monthly hours
  • Same person, every month
  • Cancel any time

Stack & Integrations

What I Develop On (and Around)

Payment gateway integration and API integration services aimed at the tools SaaS teams actually use.

Providers

  • Stripe
  • Authorize.Net
  • PayPal
  • Razorpay
  • PayU

CRM & Sales

  • HubSpot
  • Zoho
  • Opportunity

Ecommerce

  • WooCommerce
  • Shopify

Backend

  • Node / TypeScript
  • PHP
  • PostgreSQL

Ops

  • Queues
  • Webhooks
  • Reconciliation jobs

4–6 wk

To first shippable billing slice

17+

Years developing billing systems

1,000+

Recurring subscribers on one build

1

Senior engineer on your account

Development In Practice

For an agency running 1,000+ monthly recurring subscribers, I developed a full recurring billing software stack on Authorize.Net — tokenised payments, subscription lifecycle, webhook automation, dunning, reconciliation, and HubSpot data sync — replacing a manual finance workflow that had grown into a full-time job.

~90% less administrative effort · zero manual invoicing after cutover

Common Questions

Things Founders Ask Before We Start

How is this different from just using Stripe Billing?

Stripe Billing is a great starting point. I get called in when it stops being enough: hybrid pricing, multi-provider needs, self-serve flows Stripe doesn't expose, tax rules Stripe won't own, or an enterprise deal that needs invoicing outside the Stripe world. Subscription billing platforms built on top of Stripe (or alongside it) are a common outcome, not a full replacement.

How fast can we see a working billing slice?

4 to 6 weeks for a first shippable slice on most engagements. That covers plan CRUD, one provider checkout, a webhook handler with idempotency, and a reconciliation job. Slices grow from there.

Do you help migrate off an existing billing tool?

Yes. Shadow-run the new subscription billing platform against the old system, migrate customers in cohorts, watch reconciliation match, then cut over. No big-bang cutovers.

Do you work with our existing engineers?

Usually, yes. I embed alongside your team, pair on the tricky parts, and leave documented code and tests so a mid-level engineer can maintain the platform after launch.

Where does the code and hosting sit?

In your account, in your repository, under your control. Everything I develop is yours — no proprietary runtime, no licence, no lock-in.

Let's Scope Your Subscription Billing Build

Tell me what you're trying to ship, when you need it live, and where your current setup is fighting your roadmap. I'll come back with a realistic first slice, a timeline, and an honest read on what should be custom versus what shouldn't.

Book a Discovery Call

No pitch. If you don't need custom development, I'll say so.