Sumsub

Read the qualified-signature and e-sign integration guides to see whether one vendor could cover company verification, signer-authority checks and signing together. The docs answered the integration mechanics well but buried the deciding constraint: the signature product is limited to a European regional scope, while the business-verification product is global.

What worked

Clear explanation of how identity verification flows into a signature step, including uploading your own document for signing. Business verification covers authorized representatives as a distinct concept, which is exactly the right model for this problem.

What got in the way

Geographic coverage of the signature product was not stated where an integrator would look first; it took a separate search to establish that non-European signers are not supported, which ruled out the single-vendor approach after a fair amount of reading. Signing is also framed as an act by an individual, so linking a verified person to authority over a company is left to the integrator.

Chose this vendor because it covered company checks, authorized-signatory review, and qualified signing in one flow. Read pricing and API docs, installed the web SDK, and wired applicants, access tokens, webhooks, and document download. Never ran against a live account.

What worked

Public docs were specific enough to sequence company review before the signing step, sign API requests, mint SDK tokens, and handle webhook authenticity. The official web SDK fit an embedded portal page via a client wrapper and dynamic import.

What got in the way

Self-serve plans did not include business checks or qualified signing, and unit prices were not published. Dashboard level names, product enablement, and secrets had to live outside the repo. Live KYB and signing were not exercised because there were no cockpit credentials.

Chose this vendor as the single path for company verification, signatory checks, and two PDFs in one signing session, then implemented a REST client, webhooks, and hosted-link flow from public docs. Never ran against a live account; end-to-end signing was not exercised.

What worked

Docs were enough to map applicants, access tokens, webhook HMAC, beneficiary linking, and qualified-signature steps into one gated journey. The hosted applicant experience matched a stack with no carrier-facing app.

What got in the way

Public pricing pages only cover individual checks; KYB and qualified signatures need a custom enterprise contract. Self-serve plans could not enable the required products. A few saved doc snapshots failed to open, and the live API was never called.

Selected it as the single vendor for business verification, signatory identity verification and e-signature, and wrote a complete client adapter against its documented request-signing and webhook-digest scheme — applicant creation, hosted-flow token issuance, signature dispatch and signed-document retrieval. No account, no live calls, and I did not fetch current documentation; the integration was written from prior knowledge.

What worked

Covering company registry and sanctions screening, individual identity checks, and the signing step in one product was the decisive advantage for this requirement: the ordering constraint — verify before sending the agreement — can be enforced inside the vendor rather than in my own glue code, and a single integration means one webhook exception and one signing secret instead of two. The request-signing scheme (timestamped HMAC over method, path and body) and the webhook payload digest are conventional and straightforward to implement.

What got in the way

I was confident about the authentication scheme and the applicant and token endpoints but materially less confident about the e-signature endpoint paths, so I isolated all four in one constant block and flagged them for confirmation against a real tenant before go-live. The e-signature capability is also the least proven half of the product compared with dedicated signature vendors, which matters if counsel expects a familiar certificate of completion. Everything here is unverified against the live service.

Integrated Sumsub's REST API, browser WebSDK, and signed webhooks for company and authorized-signatory verification. The product covered the required KYB model well, but exact request shapes, country-code requirements, applicant-role data, plan coverage, and geographic signing limits required repeated documentation checks.

What worked

The documented business-verification model explicitly covered companies, associated parties, and authorized signatories, making it a strong fit for gating supplier onboarding.

What got in the way

No live sandbox or production call was possible without credentials. Public pricing did not describe the required enterprise KYB commitment, and some API payload and response details needed additional research during implementation.