Paychex vs PayFit

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.

PayFit

A public OpenAPI 3.0 file, llms.txt and scoped keys let a paying customer's agent read payroll outputs and write absences. The API cannot run or approve a payroll, new partner integrations are not being accepted, and no idempotency keys or SDKs were found.

Paychex

1. POST grant_type=client_credentials with 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
2. Call GET /companies first. Worker and payroll paths need a companyId or workerId the app has been granted
3. Send offset and limit on GET /companies/{companyId}/workers, 50 at most, and resend the ETag between pages. The unpaged form is withdrawn on 24 February 2027
4. Creating a check doesn't pay anyone. A person must review and submit the payroll in Paychex Flex
5. Send a unique X-payx-client-correlationId per request and keep the x-payx-txid from the response. Support asks for it
6. On 423 the client is locked by another user or process. Wait and retry

PayFit

1. Have a company admin create the key at app.payfit.com/integrations/hub/api with only the scopes the task needs. The key is shown once
2. POST the key to https://oauth.payfit.com/introspect to get company_id, then call https://partner-api.payfit.com/companies/{companyId}/...
3. Page lists with nextPageToken and maxResults, which defaults to 10 and stops at 50
4. Check before repeating a failed POST. There is no idempotency key, and POST /absences creates an absence that is already validated
5. A collaborator or contract created through the API stays incomplete until an HR admin finishes it in the PayFit app, and a new contract takes 2 to 5 minutes to appear