Short answer: no — Dataverse autonumber will NOT backfill existing rows.
This is by design, and there’s no setting to change that behavior.
But there is a clean, supported way to achieve what you want.
Why autonumber doesn’t work on existing rows
When you add an Autonumber column in Dataverse:
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It only fires on record creation
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Existing records remain blank
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The counter starts from the seed onward, but only for new rows
Dataverse deliberately avoids retroactively changing existing data to prevent:
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audit issues
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ordering assumptions
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concurrency conflicts
So you cannot tell Dataverse:
“Fill 1–100 for what already exists.”
✅ Correct and supported approach
You need to do this in two phases.
🔹 Phase 1 — Populate existing rows (1–100)
Option A (recommended): Power Automate
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Create a temporary Number column (e.g. LegacySequence)
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Create a flow:
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Trigger: Manual or scheduled
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List rows from the table
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Sort by Created On (or whatever order you want)
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Loop with an index
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Update each row with values 1, 2, 3, …
Example logic:
Initialize variable Counter = 1
For each row:
Update row → LegacySequence = Counter
Increment Counter
This gives you deterministic numbering.
Option B: Excel export/import (quick but less elegant)
Still supported, just more manual.
🔹 Phase 2 — Add Autonumber for future rows
Now:
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Add your Autonumber column
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Configure it to start at 101
Example:
Format: {SEQNUM}
Seed: 101
From this point forward:
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New records get 101, 102, 103…
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Old records keep their legacy numbers
🔹 Phase 3 — (Optional) Unify into one column
If you want one single column:
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Copy LegacySequence into the new autonumber column for existing rows
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Lock the column (read-only)
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Delete the temporary column
⚠️ Note: This requires updating the autonumber column via API/flow before locking it.
Important caveats (don’t skip this)
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Autonumber does not guarantee gap-free values
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Deletions will leave gaps
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Concurrent inserts may skip numbers
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Autonumber is for identifiers, not ordering logic
If you need strict ordering, use:
❌ What will NOT work
Dataverse will not retro-trigger autonumber.
Summary
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🔒 Dataverse autonumber never backfills existing rows
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✅ Populate existing rows via Flow or import
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✅ Start autonumber at 101 for new rows
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✅ This is the only supported, production-safe method
