# Vertex O Series vs Zamp

> Vertex O Series scores 54.7 (C) on agent readiness against Zamp's 49.5 (D), and leads in 4 of 7 scored categories. Zamp leads on reliability, agent ergonomics and payments & pricing. Both do tax calculate. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/vertex-tax-vs-zamp
- Markdown: https://www.anchorterminal.com/compare/vertex-tax-vs-zamp.md (~2,300 tokens)
- Slim: https://www.anchorterminal.com/compare/vertex-tax-vs-zamp.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/vertex-tax-vs-zamp.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-08

Vertex O Series scores 54.7 (C) on agent readiness against Zamp's 49.5 (D), and leads in 4 of 7 scored categories. Zamp leads on reliability, agent ergonomics and payments & pricing. Both do tax calculate.

- Vertex O Series: grade C, 54.7/100, rank #526 of 722. Markdown https://www.anchorterminal.com/tools/vertex-tax.md · JSON https://www.anchorterminal.com/api/v1/tools/vertex-tax.json
- Zamp: grade D, 49.5/100, rank #609 of 722. Markdown https://www.anchorterminal.com/tools/zamp.md · JSON https://www.anchorterminal.com/api/v1/tools/zamp.json

## Which one, for what

### Vertex O Series (C)

Good for: An agent working inside a company that already has an O Series licence, for quotes, invoice tax, tax area lookups and tax configuration across sales tax, use tax and VAT.

Ahead on:
- Schema & documentation, 74 against 44
- Security & auth, 57 against 40
- Maintenance & community, 62 against 42
- Transparency & trust, 68 against 50

Watch for: No public price, free tier or self-serve signup. The security guide sends new users to the Vertex sales team for an account

### Zamp (D)

Good for: An agent working for a US or Canadian seller that wants Zamp's team to register, file and remit, and needs calculation and transaction sync through a small API.

Ahead on:
- Reliability, 72 against 65
- Agent ergonomics, 64 against 51
- Payments & pricing, 20 against 0

Also in its favour:
- Free to start without a card

Watch for: No OpenAPI file for the API. The one file on the docs host is the documentation platform's plant store sample


## Score by category

| Category | Weight | Vertex O Series | Zamp | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 65 | 72 | Zamp +7 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 74 | 44 | Vertex O Series +30 |
| Agent ergonomics | 13% (16.2 this run) | 51 | 64 | Zamp +13 |
| Security & auth | 14% (17.5 this run) | 57 | 40 | Vertex O Series +17 |
| Payments & pricing | 10% (12.5 this run) | 0 | 20 | Zamp +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 62 | 42 | Vertex O Series +20 |
| Transparency & trust | 7% (8.8 this run) | 68 | 50 | Vertex O Series +18 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **54.7 · C** | **49.5 · D** | |

## Facts side by side

| Fact | Vertex O Series | Zamp |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Vertex, Inc. | Zamp Inc. |
| Hosted endpoint | `https://calcconnect.vertexsmb.com/vertex-ws/v2` | `https://api.zamp.com` |
| Transports | HTTP | HTTP |
| Auth | OAuth | API key |
| Pricing | Paid | Paid |
| x402 | no | no |
| Licence | Proprietary service under a customer agreement with Vertex, Inc. that isn't published | Proprietary service under Zamp's Standard Terms and Conditions, which form part of a signed Order Form. The sandbox has its own Developer trial terms |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| Last release | 2026-09-25 | 2026-08-31 |
| Terms last updated | no date given | no date given |
| Privacy policy last updated | no date given | 2025-02-11 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | yes |
| Terms restrict benchmarking | not found in the text | yes |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |

## Verdicts

**Vertex O Series.** Public OpenAPI 3.0 specs cover calculation, transaction management, tax area lookup and tax configuration, and guides are served as Markdown. Access needs a sales contract. No price, free tier, sandbox signup, calculation rate limit, idempotency key or official SDK was found in the reviewed documentation.

**Zamp.** A free 30-day sandbox key needs no card or sales call, and the docs are served as Markdown with llms.txt and a published limit of 1,000 requests a minute. There is no OpenAPI file, SDK, API changelog or published price, production keys come with a sales-led account, and the site footer says SOC 2 compliance is in progress.

## Before you call either

### Vertex O Series

1. Cache the access token for its 3,599-second life. The standard token endpoint allows 10 requests per 8 hours, and tokenguard.vertexcloud.com returns a cached token
2. Send no `Authorization: Bearer` header to /oauth/token, and put the client id and secret in the body or a Basic header. Credentials in the URL are rejected
3. Set `saleMessageType` to QUOTATION for an estimate. INVOICE is stored for reporting and remittance
4. Call GET /v2/transaction-exists/{transactionid} before retrying a failed INVOICE. No idempotency key is documented
5. Delete, reverse or roll back a Cloud transaction within 90 days of calculation. Later requests can cause calculation errors or duplicates

### Zamp

1. Call `POST /calculations` for a quote and `POST /transactions` only when the sale is final. Put the returned `taxDue` in `taxCollected` when posting
2. Keep transaction and line item ids to 25 characters. A repeated `POST /transactions` with an existing id returns 409 `CONFLICT`, so a retry doesn't create a second record
3. For a refund, post a new transaction with `parentId` set to the sale's id and a negative `quantity`. Never send a negative `amount` on a line item
4. Send `shipToAddress.state` and `country` set to CA for Canadian orders. `POST /addresses` validates US addresses only
5. Page lists with `limit` (1 to 100, default 10) and `cursor` until `nextCursor` is null. `GET /transactions` returns only transactions written with the same key
6. Don't store sensitive or personal data in the sandbox. Trial data is deleted after 30 days and the trial terms forbid live customer data

## Questions

### Which is better for AI agents, Vertex O Series or Zamp?

Vertex O Series scores 54.7 (C) on agent readiness against Zamp's 49.5 (D), and leads in 4 of 7 scored categories. Zamp leads on reliability, agent ergonomics and payments & pricing.

### Do Vertex O Series and Zamp need an API key?

Vertex O Series uses an OAuth sign-in. Zamp needs an API key.

### Can an agent call Vertex O Series and Zamp without installing anything?

Yes. Vertex O Series has a hosted endpoint at https://calcconnect.vertexsmb.com/vertex-ws/v2 and Zamp at https://api.zamp.com.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/vertex-tax-vs-zamp.json, and with the fewest tokens: https://www.anchorterminal.com/compare/vertex-tax-vs-zamp.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "vertex-tax", "b": "zamp"}`. From a terminal: `anchor compare vertex-tax zamp`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/vertex-tax.json and https://www.anchorterminal.com/api/v1/tools/zamp.json

## Other comparisons with Vertex O Series or Zamp

- [Anrok vs Vertex O Series](https://www.anchorterminal.com/compare/anrok-vs-vertex-tax.md)
- [Anrok vs Zamp](https://www.anchorterminal.com/compare/anrok-vs-zamp.md)
- [Avalara AvaTax vs Vertex O Series](https://www.anchorterminal.com/compare/avalara-vs-vertex-tax.md)
- [Avalara AvaTax vs Zamp](https://www.anchorterminal.com/compare/avalara-vs-zamp.md)
- [Fonoa vs Vertex O Series](https://www.anchorterminal.com/compare/fonoa-vs-vertex-tax.md)
- [Fonoa vs Zamp](https://www.anchorterminal.com/compare/fonoa-vs-zamp.md)
- [Kintsugi vs Vertex O Series](https://www.anchorterminal.com/compare/kintsugi-vs-vertex-tax.md)
- [Kintsugi vs Zamp](https://www.anchorterminal.com/compare/kintsugi-vs-zamp.md)
- [Numeral vs Vertex O Series](https://www.anchorterminal.com/compare/numeral-vs-vertex-tax.md)
- [Numeral vs Zamp](https://www.anchorterminal.com/compare/numeral-vs-zamp.md)
- [Quaderno vs Vertex O Series](https://www.anchorterminal.com/compare/quaderno-vs-vertex-tax.md)
- [Quaderno vs Zamp](https://www.anchorterminal.com/compare/quaderno-vs-zamp.md)
- [TaxCloud vs Vertex O Series](https://www.anchorterminal.com/compare/taxcloud-vs-vertex-tax.md)
- [TaxCloud vs Zamp](https://www.anchorterminal.com/compare/taxcloud-vs-zamp.md)
- [TaxJar vs Vertex O Series](https://www.anchorterminal.com/compare/taxjar-vs-vertex-tax.md)
- [TaxJar vs Zamp](https://www.anchorterminal.com/compare/taxjar-vs-zamp.md)