The vendor demo never shows you the part where two eQMS instances live side by side for 18 months, fighting over which one owns the same document number.
I learned this when we got serious about leaving our current eQMS eighteen months ago. We evaluated three platforms, ran pilots, scored APIs, and very nearly signed a contract. The thing nobody — sales engineer, implementation consultant, or RFP reference — put in writing was the parallel-system tax. The chunk of work that sits between "kickoff" and "go-live with confidence" where you're paying for two licenses, doing double data entry, and arguing with your own team about which system owns the truth.
The 18-month figure nobody quotes
In talking to peers who've actually migrated — three at peer Class II companies, one at a Class III implant maker — the realistic parallel window lands somewhere between twelve and twenty-four months. The longer end is when you have a large design history file or a heavy validation footprint under 21 CFR Part 11 and EU MDR Annex XI. Eighteen months kept coming up as the rough midpoint in casual conversation, which lined up with our own internal estimate once we priced in real document migration rather than the demo scenario.
The variables that stretch the window:
- Number of controlled document types and existing DHF volume
- Whether you migrate historical CAPAs or close them out in the legacy system first
- The validated state of legacy electronic records and signatures
- How clean your existing data model really is (it isn't)
- Your audit cycle — if you're mid-cycle, you almost certainly extend the window to keep evidence stable
What "parallel" actually looks like
The first ninety days feel productive: data mapping, taxonomy alignment, integration discovery. The next six months are the slog. You're writing SOPs that reference both systems, training users on which workflow to use when, and fielding tickets like "I can't find the CAPA I started last week." New work goes in the new system because that's the future. Old work — open CAPAs, in-flight change orders, active design reviews — stays in the legacy system because migrating in-flight records is a nightmare under ISO 13485 clause 4.1.6 and the validation expectations that come with it.
The worst part isn't the cost of two licenses. It's the period — usually month four through month nine — where your QA team is effectively running two systems, half-trained on each, and people start quietly working in whichever one is faster. That drift is what creates findings later.
The validation debt no one itemizes
Here's where it gets thorny. Under 21 CFR Part 11 and the EU MDR expectations on QMS software validation, you're not just switching tools — you're re-validating a process the old tool supported. If your new vendor provides a validation package (IQ/OQ scripts, traceability matrices), great. You still own the PQ. You still own the data migration validation, which means proving every record you moved retained its integrity, signatures, audit trail, and effective date.
The conversation I wish I'd pushed harder on eighteen months ago: what does the vendor commit to in writing about data migration validation? Which records get re-validated, and which get "converted as-is"? In our case the answer was "as-is, your problem" dressed up in friendlier language. We never got past the pilot, so we never tested whether that promise held at scale.
What I'd put in the contract next time
If we ever seriously revisit this, here's what I'm asking for before signature:
- A written parallel-run plan with named milestones, not a Gantt-shaped PowerPoint
- Explicit ownership of data migration validation — vendor, customer, or shared, with deliverables per record class
- A clause on legacy CAPA migration: does the new system preserve state, history, and effective dates without manual re-entry?
- Two cycles of internal audits against the parallel system before cutover, paid for by whom
- A real rollback path if the new system fails acceptance — because if it does, you're six months in and still paying for both
None of these are dealbreakers on their own. Together they are the difference between a migration that survives an MDSAP audit and one that produces the kind of observation you spend the next cycle explaining.
The question I'm still sitting with
The honest part: I'm not sure the eQMS market has a clean answer for this beyond "it depends on your data." And maybe it doesn't — parallel runs might just be the cost of doing this responsibly, like IQ/OQ on a new CMM. But if you've been through a real migration at a Class II or III device company, I'd love to know:
What was your actual parallel-run window, and what surprised you most about it?
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