New accountancy clients often stall between signature and first value. Documents arrive late, nobody owns the bank feeds, and the first payroll run is booked without a plan. This guide sets out the welcome, the documents needed with their due dates, the key tax dates, how the two firms communicate, and the fees, all in one shared document.

The sample shows a fictional rollout in which Kettleby Systems onboards Brackley Tax Ltd, an accountancy practice. Milestones run from kickoff on 17 March 2027 to go-live on 8 May 2027, with a fixed set-up fee and a monthly retainer. Replace the client name, owners, dates and fees with your own, then send the plan for signature before any data moves.