diff --git a/apps/edr-freight-api/src/modules/eims/eims-signer.service.ts b/apps/edr-freight-api/src/modules/eims/eims-signer.service.ts
index babec6b44..b91f306ab 100644
--- a/apps/edr-freight-api/src/modules/eims/eims-signer.service.ts
+++ b/apps/edr-freight-api/src/modules/eims/eims-signer.service.ts
@@ -8,9 +8,14 @@ import { EimsSignedRequest } from "./eims.types";
  *
  *   1. compact `JSON.stringify` of the **inner** request object only,
  *   2. those exact UTF-8 bytes,
- *   3. RSA + SHA-512 (`SHA512withRSA`, PKCS#1 v1.5 — Node's default RSA padding),
+ *   3. RSA + SHA-512 (`SHA512withRSA`, PKCS#1 v1.5 — Node's default RSA padding). Confirmed, not
+ *      assumed: MoR's own "Guide to Generating and Using Certificate for E-Invoicing" names
+ *      `SHA512withRSA` explicitly, which is PKCS#1v1.5 in Java (PSS would be named
+ *      `SHA512withRSAandMGF1`) — the same padding `createSign("RSA-SHA512")` uses by default.
  *   4. base64 of the raw signature bytes (256 bytes for an RSA-2048 key),
- *   5. base64 of the certificate file's exact bytes.
+ *   5. base64 of the certificate file's exact bytes. Also confirmed by the same guide: its own
+ *      worked example certificate is the identical `Subject:`/`Issuer:` header + 3-cert PEM chain
+ *      text-file format ours is, base64'd with no re-encoding.
  *
  * The outer `{request, signature, certificate}` envelope is never itself signed, and the request
  * object is never mutated after serialization.