Head to head · Payroll employees · October 2026 research run
Check vs Paychex
Check scores 67.5 (B) on agent readiness against Paychex's 44.8 (E), and leads in every scored category. Both do payroll employees.
Which one, for what
Check B
Good for A software platform that wants to sell US payroll inside its own product and can sign a partnership, with Check handling tax calculation, money movement and filings.
Ahead on
- Reliability, 80 against 41
- Schema & documentation, 78 against 66
- Agent ergonomics, 83 against 54
- Security & auth, 74 against 58
- Payments & pricing, 5 against 0
- Maintenance & community, 72 against 26
- Transparency & trust, 62 against 54
Also in its favour
- A hosted endpoint, with nothing to install
Watch for
No public price and no self-serve signup. The documentation says to request an API key through Check's sales contact
Paychex E
Good for A software partner with shared customers on Paychex Flex that needs to sync workers, pay rates, direct deposits and tax setup, or to send hours and earnings into pay entry.
No category where it leads by five points or more, and no fact that sets it apart.
Watch for
Partner access needs a questionnaire, review by the Corporate Partnerships Team, a demo and final approval. The sandbox is issued only after approval
Score by category
| Category | Weight this run | Check | Paychex | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 80 | 41 | Check +39 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 78 | 66 | Check +12 |
| Agent ergonomics | 13%16.2 | 83 | 54 | Check +29 |
| Security & auth | 14%17.5 | 74 | 58 | Check +16 |
| Payments & pricing | 10%12.5 | 5 | 0 | Check +5 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 72 | 26 | Check +46 |
| Transparency & trust | 7%8.8 | 62 | 54 | Check +8 |
| Negative events | ≤15 | 0 | 0 | |
| Total | 67.5 · B | 44.8 · E |
Facts side by side
| Fact | Check | Paychex |
|---|---|---|
| Kind | HTTP API | HTTP API |
| Vendor | Check Technologies, Inc. | Paychex, Inc. |
| Hosted endpoint | https://api.checkhq.com | no (local only) |
| Transports | HTTP | HTTP |
| Auth | OAuth or key | OAuth |
| Pricing | Paid | Paid |
| x402 | no | no |
| Licence | Proprietary service under Check's terms of service and partner agreement. The MCP server and CLI on GitHub are MIT | Proprietary service. Public use is under the Paychex User Terms of Use. Partner terms aren't published |
| Read-only variant documented | yes | no |
| llms.txt | yes | no |
| Last release | 2026-10-07 | 2026-08-20 |
| Terms last updated | 2021-09-03 | no date given |
| Privacy policy last updated | 2024-04-18 | 2026-06-01 |
| Customer content may train models | not found in the text | yes |
| Terms restrict automated access | yes | yes |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | not found in the text | yes |
| Arbitration or class-action waiver | not found in the text | yes |
| Popularity | 18 stars | none |
Verdicts
Check
Graded as embedded payroll through a partner API key, not access to an existing employer's payroll account. The API has idempotency keys on writes, a required preview before approval and queryable request logs. No price is public, a sandbox key comes through Check's sales team, and one API key carries the whole partner account.
Paychex
A public OpenAPI 3.0.3 definition covers 110 operations, and payroll entries stay unprocessed until a person submits the payroll in Flex. Partner credentials and the sandbox follow approval by Paychex, no price is published, and no status page, SLA or SDK was found in the reviewed pages.
Before you call either
Check
- Use https://sandbox.checkhq.com with the sandbox key and https://api.checkhq.com with the production key. A key is not valid across environments
- Preview a payroll before approving it, then pass
preview_started_atto POST /payrolls/{id}/approve so a stale preview fails with 409 - Send
X-Idempotency-Keyon every write. Keys expire after 24 hours, so list the resource before retrying later than that - On 429 wait for
Retry-After. The limit is 10 requests a second in sandbox and for partners paying fewer than 1,000 payees a month, with 100 concurrent requests - Connect the MCP server with
?read_only=trueorX-MCP-Readonly: trueunless writes are intended. In production, approving a payroll moves money
Paychex
- POST
grant_type=client_credentialswith the key and secret in the form body to/auth/oauth/v2/token. Tokens last 60 minutes and there is no refresh token, so request a new one - Call GET
/companiesfirst. Worker and payroll paths need acompanyIdorworkerIdthe app has been granted - Send
offsetandlimiton GET/companies/{companyId}/workers, 50 at most, and resend theETagbetween pages. The unpaged form is withdrawn on 24 February 2027 - Creating a check doesn't pay anyone. A person must review and submit the payroll in Paychex Flex
- Send a unique
X-payx-client-correlationIdper request and keep thex-payx-txidfrom the response. Support asks for it - On 423 the client is locked by another user or process. Wait and retry
Questions
Which is better for AI agents, Check or Paychex?
Check scores 67.5 (B) on agent readiness against Paychex's 44.8 (E), and leads in every scored category.
Do Check and Paychex need an API key?
Check takes an API key or an OAuth sign-in. Paychex uses an OAuth sign-in.
Can an agent call Check and Paychex without installing anything?
Check has a hosted endpoint at https://api.checkhq.com. No hosted endpoint is listed for Paychex.
Other comparisons with Check or Paychex
Machine-readable
- This page as Markdown
/compare/check-payroll-vs-paychex.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/check-payroll.json·/api/v1/tools/paychex.json - From a terminal
anchor compare check-payroll paychex(the CLI) - Over MCP
compare_tools {"a": "check-payroll", "b": "paychex"}at/mcp, no key