What is billing attestation?

Billing attestation is the process of cryptographically signing and chaining billable events so they can be independently verified by any party — without relying on a vendor's self-reported data.

How does Proof Meter work?

Your agent calls an API. The Proof Meter SDK captures the metadata. Proof Meter hashes, signs with ed25519, and appends it to a tamper-evident Merkle chain. The signed receipt is returned immediately and can be verified by anyone at any time.

What kinds of events can Proof Meter attest?

Any billable event — LLM API calls, vision inference, search queries, compute jobs, data transfers, or any metered service. Proof Meter is format-agnostic.

Does Proof Meter require blockchain?

No. Proof Meter uses a Merkle chain stored in Postgres with ed25519 signatures. Blockchain anchoring is on the roadmap but not required for strong tamper-evidence.

PROOF METER

by VerifiedState

INCOMING EVENTS

→

PROOF METER

RECEIPTS SIGNED 0

SPEND ATTESTED $0.00

VERIFIED RECEIPTS

←

Simulation — your receipts appear here once you start attesting.

Billing attestation for AI spend.

Every LLM call, API hit, and compute event — signed, capped, and independently verifiable.

Get API Keys → Read the docs →

How It Works

Three steps. Zero trust assumptions.

{ }

Step 1

Instrument

Add one SDK call after any billable event. Capture provider, model, tokens, cost.

typescript

import { ProofMeter } from '@verifiedstate/sdk';

const meter = new ProofMeter({ apiKey: 'vs_...' });

// After any billable event
const receipt = await meter.spend({
  provider: 'openai',
  model: 'gpt-4o',
  inputTokens: 2048,
  outputTokens: 512,
  costCents: 4.2,
});

Step 2

Attest

Proof Meter hashes, signs with ed25519, and chains the receipt in a tamper-evident Merkle chain.

json

{
  "receipt_id": "rcpt_7f3a...",
  "chain_position": 4829,
  "hash": "sha256:e3b0c44...",
  "prev_hash": "sha256:a1c9f2...",
  "signature": "ed25519:Mj7k...",
  "status": "verified",
  "verified_at": "2026-04-03T..."
}

✓

Step 3

Verify

Anyone can verify any receipt at any time. No vendor trust required. Public verification endpoint.

Try the Verifier →

Use Cases

Built for Any Billable Event

AI Agent Spend Control

Cap and audit every dollar your agents spend on LLM calls, tools, and APIs.

API

API Reseller Billing Proof

Give customers cryptographic proof of every metered API call you invoice.

Healthcare Compliance

Tamper-evident audit trail for every AI-assisted clinical decision and billing event.

∞

Autonomous System Accountability

Every autonomous action logged with cryptographic proof for post-hoc review.

≈

Cross-Provider Reconciliation

Reconcile spend across OpenAI, Anthropic, Google, and any other provider with one chain.

Pricing

Included With Every VerifiedState Plan

Proof Meter is a product line within VerifiedState. One subscription covers both.

Your VerifiedState plan includes Proof Meter receipts. No separate billing.

Free

/month

1,000 Proof Meter receipts/mo

50,000 assertions/mo

ed25519 signatures

Merkle chain

Public verification

Get Started

Pro

$29

/month

100,000 Proof Meter receipts/mo

1M assertions/mo

Everything in Free

Webhook notifications

Dashboard analytics

Get Started

Enterprise

Custom

Unlimited receipts

Unlimited assertions

SLA guarantee

Dedicated support

Data residency

Start attesting in 5 minutes.

Free: 50,000 assertions + 1,000 Proof Meter receipts/month. No credit card.

Get Free API Key Read the Docs Talk to Enterprise Sales

Early access · For development and testing · Not certified for production use in regulated industries without independent compliance review

Protected under US Provisional Patent 63/815,284