Usage-based, hybrid,or seat-based —all of it correctly.

A billing system is the logic between usage and the bank.

Your payment provider moves money. Your billing system decides how much, for what, and why — turning raw activity into priced line items, accurate invoices, successful charges, and numbers your finance team can close the books on.

It's metering, rating, invoicing, payments, dunning, tax, and reconciliation — built so every charge is provable and every dollar is accounted for.

usage → rating → invoice → cash

Every pricing model, composed onto one invoice.

Real products rarely pick one model. We build a rating engine that composes subscriptions, seats, usage, tiers, and credits cleanly — so you can change pricing without rebuilding billing.

$/month

Flat Subscription

Fixed recurring price per plan, monthly or annual, with trials and renewals.

$/seat

Per-Seat

Charge by active members or licenses, with mid-cycle seat changes prorated.

$/unit

Usage / Metered

Bill measured consumption — API calls, compute, tokens, GB — from an event ledger.

$/tier

Tiered

Different unit prices per tier as usage crosses thresholds within a period.

bulk $

Volume

A single price-per-unit chosen by the total volume reached — bulk discounts done right.

base + usage

Hybrid

A base subscription plus seats plus metered overage — composed onto one invoice.

wallet

Prepaid Credits

Customers buy credits up front; usage draws down a balance with top-ups and expiry.

free → paid

Freemium + Overage

A free included quota, then metered overage — the modern PLG monetization curve.

The pipeline from event to general ledger.

Every charge travels the same path: a metered event is rated against your pricing, rendered into an invoice, charged through the provider, then reconciled back against the books — idempotently, every step.

events ▸ meter ▸ rate ▸ invoice ▸ charge ▸ reconcile ▸ ledger // one path, idempotent end to end

Count every billable event exactly once.

Metering is the foundation usage-based billing stands on. If an event is dropped you under-charge; if it's counted twice you over-charge and lose trust. We build an idempotent pipeline where every unit is recorded once and traceable forever.

meter.ingest()

{ event: "api.call",
qty: 1, key: "req_8fa2…",
ts: 1718e9 } ✓ counted

Idempotency keys on every event

Deduplication & replay-safety

Aggregation (sum, max, unique, last)

Time-windowed counters

Append-only usage ledger

Filters & dimensions per customer

Backfill & late-event handling

Tamper-evident audit trail

Included quotas, then overage that adds up correctly.

Give each plan an included allowance, then rate everything beyond it through clean tiers. We make the boundary math exact — no off-by-one at the quota edge, no surprise true-ups.

included: 1,000,000 calls used: 3,412,908 → overage: 2,412,908 rated across 3 tiers

Mid-cycle plan changes, computed to the day.

When a customer upgrades on day 12 of a 30-day cycle, the unused portion of their old plan is credited and the new plan is charged for the remainder. We compute it deterministically and preview it before charging.

upgrade · day 12 / 30

Starter → Pro, mid-cycle. No surprise invoice.

Proration · preview

Credit — unused Starter (18 / 30 days)−$29.40

Charge — Pro for remaining 18 days$119.40

Today's prorated total$90.00

Next renewal$199.00 / mo

// downgrade policy is configurable: apply now, or defer to period end.

Invoices customers trust — and can verify.

Every line item traces back to the exact events that produced it. When a customer asks "what is this charge?", you show them the receipt — not an apology.

Invoice

#INV-2026-04812 · Apr 2026

Amount due

$964.80

Pro plan · base (1 × $499.00)$499.00

Seats · members (14 × $12.00)$168.00

API calls · metered (2.41M)$362.40

Storage overage (120 GB)$9.60

Proration credit−$74.20

Tax (consumption, 0%)$0.00

Total$964.80

every line reconciles to its source events

Itemized invoices

Invoice preview before charge

Credit notes & refunds

Custom branding & PDF

Tax lines & exemptions

Multi-currency

Net terms & due dates

Line items trace to events

Collect what's owed — without churning good customers.

failed payment ≠ lost customer. recover ~70% of involuntary churn with smart retries + card-update prompts.

Tax as a correct line item — not a quarterly panic.

We integrate tax engines to compute the right rate by jurisdiction, apply it to invoices, handle exemptions and reverse-charge, and keep filing-ready records — so tax is calculated once, correctly, at the point of sale.

rate resolved at checkout · recorded for filing

Jurisdiction-based rates

VAT / GST / sales tax

Consumption tax (JCT)

Reverse-charge handling

Exemption certificates

Tax lines on invoices

Filing-ready records

Stripe Tax / Avalara

The numbers leadership sees — the same ones finance closes on.

MRR · ARR · NRR · churn · deferred revenue — derived from the ledger, not estimated in a slide.

Tie the provider to the books — every single day.

This is the line in the catalog that finance actually cares about. Each day we diff what the provider reports against what your accounting system recorded, and surface every break as a line item — so month-end becomes a formality, not an investigation.

daily reconciliation · 2026-04-30 provider ↔ GL

Item	Provider	Ledger (GL)	Status
Card charges	$248,120.00	$248,120.00	match
Refunds	−$3,410.00	−$3,410.00	match
Processing fees	−$7,184.48	−$7,184.48	match
Payouts	$237,525.52	$237,525.52	match
Disputed (in review)	−$240.00	$0.00	break

1 break · auto-flagged

The disputed charge is the only difference — explained, tracked, and cleared when the dispute resolves. Nothing else to chase.

Fight chargebacks with the evidence already on file.

Because every charge traces to its events, dispute evidence assembles itself. We build the workflow to respond fast, track outcomes, and feed the result straight back into reconciliation.

dispute → evidence (auto-assembled from the usage ledger) → response → outcome → books updated

The rails, the books, and everything between.

stripe / orb ↔ rating ↔ quickbooks / netsuite / xero // billing only counts if it reaches the GL

Built like money depends on it. Because it does.

Billing is the one system where "mostly works" is a liability. We engineer for correctness first — idempotency, determinism, and auditability are not features here, they are the foundation.

assert(invoice == replay(events)) // if it doesn't reproduce, it doesn't ship

What you receive.

a billing system that ties out — with the runbook finance and support actually need.

Technology we use.

the right rail for your model — Stripe for breadth, Orb / Metronome for heavy metered usage.

Example: usage → invoice → reconciled.

Recommended demo

A usage-based invoice, end to end.

events ▸ meter ▸ rate ▸ invoice ▸ charge ▸ reconcile ▸ report — with every line provable.

Who billing systems are for.

SaaS platforms

Subscriptions, seats, trials, and expansion revenue billed cleanly across plans.

Infra & API companies

High-volume metered usage — compute, requests, bandwidth — rated to the unit.

AI products

Token and inference billing with included quotas, overage tiers, and prepaid credits.

FinTech

Transaction fees, interchange, and financial-grade reconciliation and audit.

Marketplaces

Take-rates, payouts, and split billing across many buyers and sellers.

Agencies & services

Retainers, milestones, and usage add-ons invoiced and reconciled per client.

How we build billing systems.

Step 01

Billing-Model Discovery

We map your pricing, plans, usage events, quotas, and exactly how revenue should be recognized.

Step 02

Metering & Rating Design

We design the idempotent event pipeline and the rating engine for seats, tiers, quotas, and overage.

Step 03

Invoice, Tax & GL Design

We define invoices, credit notes, tax handling, and how every charge maps to the general ledger.

Step 04

Development

We build metering, rating, invoicing, payments, dunning, integrations, and reconciliation.

Step 05

Shadow Billing & QA

We run the system in parallel with test clocks and replay tests until the numbers match to the cent.

Step 06

Migration & Cutover

We migrate subscriptions and usage, then cut over with no double-charges and no lapsed accounts.

Step 07

Reconciliation & Close

We turn on daily reconciliation and tune dunning and reporting against real revenue.

What a billing system is not.

the goal: a provable, reconciled billing system — every charge traceable, every dollar accounted for.

Questions, answered straight.

Related SaaS & Product services.