Spreadsheet Risk

Multiple Users Editing the Same Excel File

Excel was built around one person owning a file. When several people need to edit the same data, you get locked files, conflicting copies and a person doing the merging by hand. Co-authoring in Microsoft 365 fixes the locking, but not the permissions, validation or history — and those are usually the real problem.

7 min readUpdated 2026-09-15

When several people genuinely need the same data at once, Datanova helps businesses move the process into a system built for concurrent users.

Why it breaks

A spreadsheet is a document. Documents assume one author at a time, and everything Excel does with shared files is an attempt to work around that assumption rather than remove it.

A file on a shared drive locks: the second person gets read-only and makes a copy instead
Copies diverge immediately, and nothing in the file records which is current
Someone becomes the merge process, reconciling by hand every week
Two people fix the same wrong number differently, and one fix silently wins
A paste over a formula column breaks calculations for everyone downstream

What co-authoring actually fixes

Excel for the web and Microsoft 365 co-authoring are a genuine improvement, and worth turning on before considering anything more expensive. Be clear about the boundary:

Problem	Does co-authoring fix it?
File locking	Yes — several people can edit at once
Copies diverging	Mostly, if nobody downloads a local copy
Who changed what	Partially — version history, not per-record attribution
Different people seeing different data	No — the file is all or nothing
Preventing bad data being entered	No — validation stays advisory
Undoing one person's change from last Tuesday	No
Performance on a large workbook	No, and often worse

If your problems are only in the first two rows, co-authoring plus a rule that nobody keeps local copies may be the whole solution. That is a free fix, and worth trying first.

The three fixes, cheapest first

Single master file with discipline — one copy on SharePoint or Google Drive, co-authoring on, protected formula ranges, edit rights restricted to the people who need them, and a standing rule against local copies. Days of effort, no cost.
Split the file by owner — give each person or site their own input file and automate the consolidation into a master nobody edits by hand. This removes the merge role without replacing anything, and is usually 1 to 3 weeks of work.
Move the data into a system — a database with a small interface, where many people write at once, permissions are per role, validation runs at entry and history is attributable. This is the only fix that reaches permissions and audit trail.

Work down that list, not up. Most teams that think they need option 3 get enough relief from option 2, and the ones that genuinely need option 3 usually know it because their problem is permissions or traceability rather than merging.

How to tell which one you need

Only conflicts and versions → option 1, and it is free
Several people producing data that has to be combined → option 2
Different people must see different rows or columns → option 3
You need to prove who changed a figure → option 3
The file feeds invoicing, payroll or compliance → option 3

Frequently asked questions

How many people can edit an Excel file at once?

With co-authoring in Microsoft 365, technically dozens — but usefully, far fewer. Beyond a handful of simultaneous editors on an operational workbook, conflicts, performance and accidental overwrites make it unworkable in practice.

Does Google Sheets handle multiple users better?

Yes, noticeably. Concurrent editing is smoother and version history is better. It does not give you per-role permissions on subsets of data, real validation, or an attributable per-record audit trail, and it slows down at volume sooner than Excel does.

Can we lock parts of the spreadsheet?

You can protect sheets and ranges, and you should — it prevents a good share of accidental damage to formulas. It is a guardrail, not a permission system: it does not stop someone seeing data they should not, and protection passwords are trivially removed.

What about Excel's shared workbook feature?

The legacy shared workbook feature is deprecated and disables many of Excel's capabilities while it is on. Microsoft's replacement is co-authoring. Do not build a process on the legacy feature.

Still merging spreadsheets by hand?

In a free consultation we look at how the file is shared today and tell you which of the three fixes your situation actually needs — including when the answer costs nothing.

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