> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kirafin.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Required documents
> How documents attach to a sub-client, what forms they take, and the limit that catches people out.
Documents are part of the sub-client you create, not a separate upload step. They attach to the record they belong to — a registration document to the business's identifying information, an identity document to the person it identifies.
## Where they attach
Every document sits inside an `identifying_information` entry, in that entry's `documents` array. A person's identity document nests under that person's entry rather than sitting loose.
Both value sets — the kinds of identifying information, and the kinds of document — are listed in [User values](/reference/users/values#identifying_information-types).
## Two ways to send a file
| Form | What it is | Use it when |
| ----------------- | ----------------------------------- | ------------------------------------------------------ |
| A base64 data URI | The file inline in the request body | The file is small |
| An `https://` URL | An address Kira fetches from | The file is over a few megabytes, or there are several |
**The whole request body is capped at 10 MB**, and inline base64 counts against it with about a third of overhead on top of the file's own size. A handful of scanned documents reaches that limit quickly — send a URL instead, which is fetched separately, does not count against the body, and may be up to 30 MB.
## Which documents
Which ones a given business needs depends on what it is and where it was formed. The sub-client tells you: `missing_fields` names what is still outstanding, grouped by product, and it is the list to work from rather than a table you keep on your side.
## When one cannot be read
If Kira cannot fetch a document you supplied by URL, `user.document.download.failed` fires. Nothing else tells you — a document that never arrived looks the same as one never sent, so handle that event rather than assuming an upload succeeded.
What happens when something more is needed.