When is the best time to migrate legacy Office files?

Q3 (July–September) is typically the best window for organizations still running Windows 10 — it provides a buffer before the October EOL deadline and allows time to resolve any post-migration issues before year-end freeze periods.

How long does a legacy file migration take?

Simple batch migrations (no VBA, no linked tables) can complete in a day. Complex environments with 500+ files, VBA modules, and linked tables typically require 4–8 weeks including discovery, testing, conversion, and validation.

Do I need to convert files that haven't been used in years?

No. Files last accessed more than 12 months ago are good candidates to archive in their original format rather than convert. Document their location, compress them, and move them to cold storage. Focus migration effort on actively used files.

What's the biggest risk in a legacy file migration?

The biggest risk is undiscovered scope — migrating without knowing how many files exist, which contain VBA, and which are linked to other databases. Running a discovery scan before planning eliminates this risk.

Q3 Legacy Migration Readiness Checklist — Are Your Files Ready for the Second Half of 2026?

April 24, 2026 · 7 min read

Q3 is the window. Windows 10 is already past its end-of-life date. Organizations that haven't upgraded to Windows 11 are running without security patches. And Q4 brings year-end freezes, holiday staffing gaps, and budget cycles that make emergency migrations miserable.

If you have legacy .xls, .xlsm, or .mdb files in production — and you haven't migrated them yet — Q3 is the time. This checklist covers everything you need to assess readiness, plan the migration, and validate the results before you flip the switch.

Print it. Share it with your IT team. Work through it in order.

How to use this checklist: Work through each section sequentially. Don't skip to conversion before you've completed the inventory. The order matters — scope creep and undiscovered complexity are what kill migration projects.

Section 1 — File Inventory

You cannot plan a migration you haven't measured. This section should be completed before any other planning work begins.

1. Discovery

Run LegacyLeaps's free scanner across all mapped network drives and shared folders Required
Include local drives on all machines that run Office workflows — not just file servers
Document total file counts by format: .xls, .xlsm, .xla, .mdb, .mde
Record VBA module counts for each file (scanner provides this)
Record linked table counts for each Access database (scanner provides this)
Note last-accessed dates — files not opened in 12+ months are archive candidates
Confirm all network share paths are accessible before the scan (authentication, permissions)

2. Triage and classification

Classify each file into one of four tiers: Archive / Simple Convert / Convert+Verify / High-Touch
Archive tier: last accessed >12 months, no linked tables — compress and document, skip conversion
Simple Convert tier: no VBA modules, no linked tables — batch process with no manual review
Convert+Verify tier: VBA modules present, no linked tables — convert, then spot-check modules
High-Touch tier: VBA + linked tables, or >10 VBA modules — convert individually with full UAT
Get sign-off from a business owner on the archive list before removing anything from scope Required

Get your inventory in 30 minutes

LegacyLeaps's free scanner discovers all legacy files across your network shares and produces the triage report automatically — file count, VBA complexity, linked tables, access frequency.

Download the Free Scanner

Section 2 — Compatibility Testing

Never batch-convert without running a test conversion first. One representative file per tier is enough to surface 90% of issues.

3. Test conversion

Select one file from each non-archive tier for test conversion
Convert the test file on the target OS and Office version (the destination environment, not your workstation)
Open the converted file and verify it loads without errors
For Excel: run all macros, check formulas, verify chart rendering
For Access: open all forms, run all queries, verify linked table connections
Compare record counts between source and converted file — they must match exactly Required
Document any issues found and determine if they require pre-conversion fixes or post-conversion remediation

4. VBA compatibility check (for Convert+Verify and High-Touch tiers)

Open VBE in each test file and scan for Declare statements without PtrSafe keyword — required for 64-bit Office
Check for deprecated API calls (e.g., CreateObject("Word.Application") patterns that rely on specific Office versions)
Verify ActiveX controls load without "object cannot be created" errors
Test any forms that use API calls for file dialogs, registry access, or Windows UI functions
Check for hardcoded file paths that will break when database is moved to new location
Run the VBA audit script from our VBA audit guide on all High-Touch files

5. Linked table verification (Access only)

Run the MSysObjects query to list all linked tables and their source paths
Confirm all source databases exist at the documented paths
Document which databases link to which — the dependency map determines conversion order
Plan to convert linked databases before the databases that link to them
Test that linked table connections survive after the source database is converted to .accdb

Section 3 — Backup and Risk Management

Backups are not optional. If you skip this section and something goes wrong, you have no recovery path.

6. Pre-migration backups

Create a full backup of all source files before any conversion begins Required
Store backups on a separate volume from the originals (different drive, different server, or external media)
Test that backup files open correctly before proceeding — a corrupt backup is not a backup
Document backup location and retention policy — how long will you keep originals after migration?
For databases with active users: coordinate a maintenance window so no one is writing to the database during conversion
Record file sizes and record counts of source files for post-migration comparison

7. Rollback plan

Define the rollback trigger: under what conditions will you revert to the original files?
Confirm the rollback procedure: where are the backups, who executes the rollback, how long does it take?
Identify the maximum acceptable downtime if rollback is needed
Communicate the rollback window to affected users before migration begins

Section 4 — User Communication

The most technically perfect migration fails if users don't know what to expect. Silent changes generate helpdesk tickets.

8. Stakeholder notification

Send written notice to all affected users at least 5 business days before migration Recommended
Include in the notice: what's changing (file names, locations, formats), when it's happening, what they need to do, who to contact
For Access databases with VBA forms: walk power users through the converted UI before cutover — don't surprise them
Identify any users who have the file open via Autorun, login script, or scheduled task — coordinate shutdown
Schedule a helpdesk surge window for the 48 hours after cutover

9. IT team coordination

Assign a single owner for each High-Touch file — someone accountable for UAT sign-off
Define escalation path if a file fails validation
Block out IT calendar for the migration window — no other major changes during this period
Document the migration log: file name, tier, conversion date, validator, sign-off status

Section 5 — Conversion Execution

10. Batch conversion (Simple Convert tier)

Run LegacyLeaps batch conversion during off-hours when files are not in use
Process one folder at a time — don't run all files simultaneously on first pass
Monitor the conversion log for any files that error or produce warnings
Do not delete source files until validation is complete Required

11. Convert+Verify tier

Convert in smaller batches of 20–30 files
Spot-check VBA modules in the highest-priority files (those used most frequently)
Confirm module count in converted file matches source (LegacyLeaps validation report provides this)
Run key macros manually before marking the file as complete

12. High-Touch tier

Convert one file at a time with a dedicated review before moving to the next
Re-link linked tables using LegacyLeaps's table re-linking tool or the VBA bulk re-link script
Conduct UAT with a business user who regularly uses the file — not just IT
Get written sign-off before cutover Recommended
Document any manual fixes applied (VBA changes, path updates, control replacements)

Section 6 — Validation

Conversion without validation is not migration — it's hope. Every file needs a passing validation before source files are retired.

13. Record count validation

Run LegacyLeaps's validation report on all converted files Required
Confirm record counts in converted .accdb/.xlsx match source .mdb/.xls exactly
Flag any file with a count discrepancy — investigate before deployment
For Excel: verify formula outputs against known reference values
For Access: run the key queries that the business depends on and spot-check output

14. Post-cutover monitoring

Monitor helpdesk tickets for the 48 hours after each batch deploys
Keep source files accessible (read-only, not deleted) for a minimum of 30 days post-cutover
Schedule a 2-week post-migration review with department heads
Document final migration log: files migrated, validation status, any exceptions
Archive the migration log in a permanent location — you'll need it for compliance questions

Q3 Timeline Reference

Week	Activity	Owner
Week 1 (Early Jul)	Run discovery scan, produce triage report, get archive sign-off	IT + Dept Heads
Week 2	Test conversion, VBA audit, linked table dependency map	IT
Week 3	Backups verified, rollback plan documented, user notices sent	IT + Dept Heads
Weeks 4–5	Simple Convert and Convert+Verify batch conversion	IT
Weeks 6–9	High-Touch migration, UAT, sign-off	IT + Power Users
Week 10	Full validation, 48-hour monitoring, migration log complete	IT
Week 11–12 (Late Sep)	2-week post-migration review, source file retention decision	IT + Management

This timeline fits a mid-size environment (200–600 files) with a 2–3 person IT team. Larger environments or high-touch file counts will need more time in weeks 6–9. Smaller environments can compress the schedule significantly.

The One Thing That Derails Q3 Migrations

Scope creep from undiscovered files.

Teams start the migration, convert 80% of the known files, and then a department head asks "what about the 40 databases in the HR shared drive?" — which nobody knew about. Now you're two weeks from the Windows upgrade, and you have 40 high-complexity Access databases with linked tables that weren't in the plan.

The scanner eliminates this. Run it first, run it everywhere, and run it again two weeks later to catch any files that were being written to when the first scan ran. The 30 minutes you spend on discovery saves weeks of reactive fire-fighting.

Start with the scan

LegacyLeaps's free scanner runs in under 30 minutes and gives you everything in this checklist's Section 1 — automatically. Download it, run it, and you'll have a migration plan before the end of the day.

Download the Free Scanner

Facing a large environment or tight deadline? Talk to us about done-for-you migration.

Related Resources

Part of the Windows Upgrade Survival Guide for Office Files.

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