If your product charges by usage — API calls, tokens, seats, whatever — you already know that billing stops being a solved problem the moment pricing gets even slightly creative. Someone has to meter usage accurately, send the invoice, chase the client who "forgot" to pay, and reconcile it all with the bank statement at month-end. A wave of new AI-powered tools now does most of that job for you: reading contracts, generating invoices, following up on late payments, and reconciling books automatically. This guide covers seven real tools doing that today, split into two groups — AI billing agents that automate the whole post-contract workflow, and AI-native metering platforms built specifically for usage-based, API-driven pricing.
The short version
If you want an agent that reads your contracts and chases payments for you, look at JustPaid or LedgerUp. If you need a full quote-to-cash platform for a growing SaaS company, Hyperline covers more ground. If you're a solo founder who just wants auth plus billing bolted together fast, Serial Subscriptions is built for exactly that. And if your real problem is metering AI usage itself — tracking API calls, tokens, and margins per customer in real time — Credyt, UnitPay, and Vayu are the three purpose-built options.
AI billing agents: automating what happens after the contract is signed
JustPaid — the AI agent that reads your contracts
JustPaid is an AI billing agent for B2B companies: it reads signed contracts to auto-extract billing terms, sends invoices, chases late payments, and reconciles payments across Stripe, bank accounts, and QuickBooks automatically. JustPaid reports an 87% collection rate from its AI-driven follow-up sequences, and is Y Combinator-backed with over $81M in payment volume processed as a track record.
Pricing: Free up to $100K in annual revenue, then Starter at $499/month, Growth at $999/month, Scale at $1,999/month, Professional at $2,999/month, and custom Enterprise pricing above $50M revenue.
Honest take: The free tier is generous for a pre-revenue product but becomes a hard wall the moment you cross $100K ARR — and the jump straight to $499/month after that is steep for a very small team. Best fit for a company already past its earliest revenue that wants contract-reading and collections automated rather than assembled from separate tools.
LedgerUp — a Slack-native AI agent for accounts receivable
LedgerUp's AI agent, named Ari, automates everything a B2B company does after a contract is signed: invoicing, chasing payments, and reconciling the books. It lives inside Slack with human-in-the-loop approvals rather than another dashboard to check, and reports reducing Days Sales Outstanding by 35% on average.
Pricing: Starter at $500/month (10,000 credits, 14-day free trial, 15% off annual billing), with Growth and Enterprise on custom quotes. Overage runs $0.12/credit on Starter or $0.09/credit on Growth, with no per-seat fees.
Honest take: $500/month plus per-credit overage isn't cheap for a small team, and the Starter plan is limited to one connected billing source and one CRM integration. It's also explicitly a complement to your existing billing system rather than a replacement for it — you're adding a tool, not consolidating your stack.
Hyperline — quote-to-cash in one platform
Hyperline covers the whole revenue cycle for SaaS companies — quotes, billing, and cash collection — instead of stitching together separate tools. It handles global invoicing compliance across 100+ countries, e-invoicing in 80+, and is SOC2, ISO27001, and GDPR certified, with 500M+ invoices reportedly processed at 99.9% reconciliation accuracy.
Pricing: Quote to Cash at $199/month plus 0.6% of revenue; Quote to Cash + Usage at $299/month plus 0.7% of revenue; custom pricing for High Volume accounts above $5M ARR. CRM/accounting integrations cost an extra $50/month each. Free trial covers 10 invoices.
Honest take: The percentage-of-revenue pricing is the thing to model carefully — at real scale, 0.6-0.7% of revenue can outpace a flat-fee competitor fast. Strongest fit for a company that genuinely needs the CPQ-to-collections consolidation and international invoicing compliance, less so for a simpler domestic subscription business.
Serial Subscriptions — auth and billing in one integration for solo founders
Serial Subscriptions handles the boring-but-critical parts of running a subscription business — logins, Stripe billing, usage limits, upgrades — in one integration, instead of a solo founder stitching together five different services. It claims a roughly 10-minute integration and automatic ASC 606 revenue recognition compliance, and it uses your own existing Stripe account rather than routing payments through a new processor.
Pricing: Developer tier is free. Starter is $25/month or $240/year (50k MAU). Business is $300/month or $3,000/year (50k MAU). Enterprise is custom. Additional users cost $0.02/user/month.
Honest take: The jump from Starter ($25) to Business ($300) for the same MAU cap is a real pricing cliff to watch for. It's also a single vendor for both auth and billing, which is convenient until you need to swap out one piece without touching the other. Good fit for an indie or early-stage founder who wants to skip assembling Auth0/Clerk plus a billing tool separately.
AI-native usage metering: billing infrastructure built for AI products
Credyt — real-time cost tracking per API call
Credyt is billing infrastructure built specifically for AI products: it tracks what each customer's AI usage actually costs in real time, per API call, model, and client, and lets you bill for it before you lose money on a runaway request. It supports budget caps with pre-authorization — blocking overages before they happen rather than billing for them after — and its team comes from Visa, Checkout.com, TrueLayer, and SumUp.
Pricing: Free to start, then $1 per active customer wallet per month, with no percentage taken on revenue and no long-term commitment.
Honest take: The flat $1/wallet pricing is genuinely predictable at volume, which is rare in this space, but it's a young product going up against more established names like Metronome, Orb, and Lago. Only worth it if your AI costs actually vary meaningfully per customer — if they don't, plain Stripe Billing is simpler.
UnitPay — free usage metering up to $500K ARR
UnitPay is billing infrastructure built specifically for AI companies: it tracks usage like API calls or tokens, generates invoices, and shows margins in real time. It integrates with existing payment processors (Stripe, Razorpay, Paddle) rather than replacing them, and claims real-time metering at 50M+ events/month with 1ms ingestion latency.
Pricing: Free, with unlimited event tracking and full features, until $500K ARR. Growth tier above that requires a sales consultation for custom pricing.
Honest take: Free until $500K ARR is unusually generous for this category, making it an easy first pick for an early-stage AI product. It's also the newest, least-proven name here compared to Metronome (acquired by Stripe for roughly $1B) or Orb, and there's no open-source or self-hosted option the way there is with Lago.
Vayu — billing plus revenue recognition for complex B2B pricing
Vayu is an AI-powered billing and revenue platform that lets a B2B SaaS company mix subscriptions, usage-based charges, and custom negotiated contract terms in one system, then handles ASC 606 revenue recognition automatically instead of a finance team reconciling it by hand. It's built specifically for the hybrid usage/subscription pricing common at modern AI and SaaS companies, and has raised $7M in seed funding.
Pricing: Not publicly listed — the site only offers "Get started" or "Book a demo," aimed at B2B companies with genuinely complex pricing (usage plus subscription plus negotiated contracts).
Honest take: No public pricing means a sales cycle before you know the real cost, and it's a young platform with less production track record than Zuora or Chargebee. Probably overkill if your pricing model is still simple — it earns its keep once you're mixing multiple pricing types across the same customer base.
| Tool | What it automates | Starting price | Best for |
|---|---|---|---|
| JustPaid | Contract reading, invoicing, collections | Free to $100K ARR, then $499/mo | Post-revenue B2B chasing late payments |
| LedgerUp | Invoicing, collections, reconciliation via Slack agent | $500/mo | Teams that want AR handled inside Slack |
| Hyperline | Quote-to-cash, global invoicing compliance | $199/mo + 0.6% revenue | SaaS companies needing CPQ + collections in one |
| Serial Subscriptions | Auth + Stripe billing bundled | Free, then $25/mo | Solo founders shipping fast |
| Credyt | Real-time per-call AI cost metering | Free, then $1/wallet/mo | AI products with per-customer cost variance |
| UnitPay | Usage metering, invoicing, margin tracking | Free to $500K ARR | Early-stage AI products on a budget |
| Vayu | Hybrid billing + ASC 606 revenue recognition | Custom quote | Complex negotiated B2B pricing |
None of these are a free lunch: every AI billing agent here still needs your existing Stripe account, bank connection, or CRM wired in correctly before it can do anything useful, and pricing that looks cheap at the free tier can turn into a real line item the moment you cross an ARR threshold or add integrations. If your billing is still simple — flat monthly subscriptions, one plan tier — you likely don't need any of these yet. But once pricing gets hybrid, usage-based, or contract-negotiated, the manual spreadsheet-and-reminder-email approach breaks fast, and these seven tools are where real teams are turning instead.