Data Cleaning & Spreadsheets
The Complete Excel Data Cleaning Checklist (Free 12-Step Audit Guide)
Marcus Vance
Principal RevOps & Data Architect
October 10, 2026 6 min read
TL;DR / Quick Summary
Our 12-step data cleaning audit checks for delimiter consistency, column header naming, null value replacement, de-duplication, phone normalization, and date formatting.
The 12-Step Pre-Import Spreadsheet Audit
Never upload a raw file to your CRM without running through this rapid audit.
Execution Checklist
Verify first row contains unique, snake_case or clean column headers.
Strip non-printable ASCII characters and UTF-8 Byte Order Marks (BOM).
Trim leading and trailing whitespaces across all text columns.
Execute fuzzy de-duplication based on primary email and phone fields.
Standardize dates to ISO 8601 format (YYYY-MM-DD).
Normalize international phone numbers to E.164 format (+XXXXXXXXXXX).
Sanitize email syntax and remove role-based addresses (support@, admin@).
Replace inconsistent NULL representations (N/A, #VALUE!, null, -) with empty strings.
Validate numeric columns contain purely numerical digits without currency symbols.
Ensure uniform title-casing for contact names and company titles.
Split composite address columns into Street, City, State, and Zip.
Verify row count against original source export to prevent silent data drop.
Frequently Asked Questions
Can Olonyn perform all 12 checklist steps automatically?
Yes! Drop your CSV into Olonyn's Data Cleaner and all 12 steps execute in under 30 seconds.
Written by Marcus Vance
Principal RevOps & Data Architect
Former data consultant who automated enterprise ETL pipelines, CSV data normalization, and B2B pipeline intelligence models.
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