Disclosure upfront: I'm a District Manager at ADP covering the DMV market, so I'll caveat where my bias might lean. With that out of the way, here's what I've actually seen at this size band:
The 60-90 day timeline reps quote is technically achievable, but only on a narrow path. It assumes you have clean data, an internal project owner with 10+ hours/week to dedicate, and you're not also re-architecting your benefits plan or 401(k) at the same time. Most 200-EE migrations I've watched land closer to 90-120 days end-to-end.
Where the timeline blows up:
- Data cleanup is almost always underestimated. Your Paychex export will have 3-5 years of legacy fields, terminated employees with incomplete records, and pay history that doesn't quite map. Budget 2-3 weeks just for data hygiene before any actual configuration starts.
- Benefits carrier integrations take longer than payroll. EDI connections with Aetna/UHC/BCBS often need 30-45 days alone, and you can't run live OE on the new platform until those land.
- Time clock migration if you have punch clocks — physical hardware swaps + employee re-enrollment add 2-4 weeks.
- The first parallel-run cycle will surface issues. Plan for at least one full payroll where you process on BOTH platforms and reconcile.
For a Paychex Flex → modern HCM move specifically (regardless of which modern HCM), realistic phases:
- Weeks 1-2: contract + kickoff + data audit
- Weeks 3-6: config + EDI setup + integrations
- Weeks 7-9: parallel run + UAT
- Weeks 10-12: go-live cutover
- Weeks 13-16: stabilization + cleanup
Where ADP Workforce Now is genuinely strong at 200 EE: tax filing reliability (we file in 47 states ourselves, not via a partner), the benefits administration integration depth, and the parallel-run tooling. Where competitors are stronger: Rippling has a better UX layer if your team skews tech-comfortable, Paylocity has a more modern reporting builder.
The practical advice independent of vendor choice: lock in your project owner before signing the contract. The single biggest predictor of on-time go-live I see is whether there's one named person with the authority and bandwidth to drive the implementation. Without that, every vendor's timeline slides 30-60 days regardless of platform.
Happy to dig into specifics if helpful.
— AJ