You can build a flawless workbook — structured, co-author-ready, refreshable — and still lose the war, because it lives in the wrong place: a laptop’s Documents folder, a personal drive shared by link with one colleague who left, or an email thread’s attachment history. Microsoft 365 gives files exactly three kinds of home, and most of the chaos in most organisations is files living in the wrong one.

The three homes

OneDrive is yours — a personal drive in the cloud. Drafts, scratch models, your own money sheets, work-in-progress nobody else needs yet. Its superpower is being personal: synced, versioned, recoverable. Its trap is the same thing: when you leave, access dies with your account, and “shared from OneDrive” is how team-critical files end up owned by ghosts.

SharePoint is the team’s — document libraries owned by a site, not a person. Anything a team depends on lives here: the monthly report pipeline’s folder, the master workbook, the Forms-fed Tables. Survives leavers, carries permissions by library or folder, and is what queries should point at — a SharePoint path outlives every individual.

Teams is — and this is the part that declutters everything — a view of SharePoint. Every Teams channel’s Files tab is a SharePoint library underneath. Posting a file “in Teams” files it there; two names, one storage. Which collapses the three-way confusion into a two-way choice: mine (OneDrive) or ours (SharePoint, possibly worn as Teams).

who needs this file if you vanish tomorrow? nobody the team OneDrive drafts · personal · WIP SharePoint the team's system of record Teams = a window one question, two homes — and "email it" is never one of them
The whole placement policy is one question about your own disappearance. Teams isn't a third answer — it's SharePoint wearing a chat interface.

The placement rules

  1. The vanish test decides. Would anyone need this file if you left tomorrow? Then it’s team property from birth — create it in SharePoint, don’t “move it later” (later never comes; leavers’ OneDrives are where reports go to die).
  2. Share the location, not a copy. Attaching a workbook to email forks it — the v7 disease in one click. Share a link (with sensible permissions), and there stays one file. Inside Teams, the same rule reads: upload to the channel, link in the chat. Files posted into private chats land in personal OneDrives — team files go in channels.
  3. Structure beats search, once. A library needs the same architecture as a workbook: predictable folders, real names (2026-07 Sales Report.xlsx, never FINAL v3— dates sort, adjectives don’t), and the discipline that a file has one home. Ten minutes of library design saves a hundred “where’s the…?” messages.
  4. Local copies are for airplanes. OneDrive/SharePoint sync is fine offline plumbing, but “I saved a copy to my desktop to work on” recreates 2009. The cloud copy is the file; version history is the undo; sync handles the train tunnel.

The payoff reaches back through the whole stack: queries that never break on a renamed path, flows that file attachments into a library that outlives everyone, dashboards whose one link is the report. Files, it turns out, obey the same law as cells: one truth, one home, everything else points at it. You learned that in stage one — it was never really about cells.