Most MSP onboardings fail in the first two weeks because the team treats onboarding as setup. It is not setup. It is a managed handoff between the prior provider, the client, and your dispatch desk. Setup is one workstream inside it.
The 47-step checklist below assumes you have a signed agreement, a project owner on your side, and a single point of contact on the client side. If you do not have those three things in place, do not start onboarding. Pause and fix that first.
Pre-flight covers documentation, asset inventory, credential transfer, change-management posture, and SLA confirmation. Most teams skip the credential transfer step or treat it as a side conversation. That is the number-one source of post-onboarding incidents in our retrospectives.
Day-0 means the day your team officially has operational responsibility. The checklist for day-0 is about getting telemetry flowing, confirming endpoints are reporting to your RMM, getting backup jobs verified, and posting an internal status update to your service desk channel.
Week-1 actions are about hardening, not heroics. Resist the urge to launch a security project in week 1. Confirm baselines first. Most clients arrive with one or two surprises in week 1 that require a calm conversation rather than a fix.
The day-90 checkpoint is the most-skipped step. It is a structured retrospective between you and the client. What worked, what did not, what surprised them, and what they want different. Day-90 is also when you upsell — a project, an additional service line, a quarterly cadence.