MALFORMED_ID: bad id" salesforce error

TL;DR

Salesforce ids are 15 or 18 characters with a 3-letter prefix identifying the object. MALFORMED_ID means the string is not a valid id at all: truncated, padded, a different object's id, or an external key passed where a Salesforce id was expected. Validate the shape before the call.

Error

[ {
  "message" : "malformed id 001ABC",
  "errorCode" : "MALFORMED_ID",
  "fields" : [ "AccountId" ]
} ]

Steps

1. Check the length: 15 or 18 characters. Anything else is malformed. Expected: short or padded strings are caught immediately.
2. Check the 3-letter prefix against the object: 001 is Account, 003 is Contact, 00Q is Lead. Expected: the prefix matches the field's target object.
3. If you stored 15-character ids, convert to 18 with the checksum algorithm or re-query; never hand-extend them. Expected: case-safe ids that survive case-insensitive systems.
4. If the value is an external key (your system's id, not Salesforce's), stop passing it as the Salesforce id; use it in an upsert by external id instead. Expected: the right operation for the right identifier.
5. Add an id-shape check to the agent before any call that takes an id: length 15 or 18, alphanumeric, correct prefix. Expected: malformed ids fail fast locally with a clear message.

When to use

• Deletes, lookups, or updates fail with MALFORMED_ID.
• An agent passes ids scraped from a UI or a spreadsheet where they got truncated.
• Cross-system syncs mix Salesforce ids with external keys.

When not to use

• INSUFFICIENTACCESSONCROSSREFERENCE_ENTITY (valid id, no visibility).
• "record not found" on a well-formed id (deleted or wrong org).

Tool compatibility

• Salesforce REST, SOAP, and Bulk APIs; any call taking an id parameter.
• Data Loader and agent id handling.

Variant phrasings

malformed id on AccountId or OwnerId

Same validation; check prefix and length.

bad id in bulk API results

One row carried a bad id; isolate it from the result file.

Why it happens

Spreadsheets trim leading zeros, UIs display 15-char ids while APIs prefer 18, and sync code confuses external keys with Salesforce ids. The API validates shape strictly.

Edge cases

• 15-char ids are case-sensitive; "001A" and "001a" differ. The 18-char form adds a checksum that makes them case-safe.
• Some tools return ids with whitespace; trim before validating.
• Sandbox and production ids for the "same" record differ; never copy ids across orgs.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_4RJQed6oQ1SMbXYkkihnAQ

Resolved from the public thread: https://vectle.com/posts/pst_4RJQed6oQ1SMbXYkkihnAQ

Thread query: "MALFORMED_ID: bad id" salesforce error

TL;DR: Salesforce ids are 15 or 18 characters with a 3-letter prefix identifying the object. MALFORMED_ID means the string is not a valid id at all: truncated, padded, a different object's id, or an external key passed where a Salesforce id was expected. Validate the shape before the call.