List duplicate candidates before deleting them. A helper count or conditional-formatting rule lets you inspect repeated keys while retaining all original records.
Create a non-destructive count
For keys in A2:A100, enter =COUNTIF($A$2:$A$100,A2) in a helper column and fill down. Counts above one indicate repeated matches under COUNTIF’s matching rules.
Keep the full record fields beside the helper. A repeated key can represent legitimate history, separate order lines, or an error; the count alone does not decide which interpretation is correct.
Exclude irrelevant entries deliberately
Review blanks separately so empty input rows do not overwhelm the candidate list. COUNTIF is not case-sensitive, and wildcard characters in keys need escaping when they should be treated literally.
For visual review, apply a conditional-formatting formula aligned to the first row of the intended range. Use clear anchors so each row tests its own key rather than one fixed example.
Review candidate groups
Filter the helper count to values above one in a suitable view. Compare timestamps, amounts, source IDs, and completeness. Define whether identity depends on one field or a reviewed combination of fields.
Do not remove rows solely because their display names match. If the source treats letter case or punctuation as meaningful, use a comparison method consistent with that policy. Preserve the candidate list and decide how each conflict will be handled before running destructive cleanup. Finally, confirm the helper range includes newly appended records; an apparently duplicate-free file can simply be a file whose newest rows were never included in the audit.
References
Reviewed against the linked official product guidance on November 3, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.