Agree on the handoff before the first run.
Ask both providers to identify the last payroll the old provider will process and the first payroll the new provider will process. Separately name who will make each remaining deposit, file each return, handle corrections, and prepare year-end forms. A payroll processing date alone does not answer those questions.
For example, a worker’s year-to-date register may agree with the company total while a voided check remains in the import. Compare worker records as well as company totals, keep the source exports, and resolve discrepancies before approving the opening balances. A balanced total is a useful check, not evidence that every worker record is correct.
Keep deposit confirmations separate from calculated tax liabilities. A report that says tax was withheld does not show that the agency received it. Preserve access to the old provider’s records until the handoff and remaining responsibilities are documented.
Source and scope
The IRS explains the different arrangements and responsibilities in Outsourcing payroll and third-party payers. Employer liability depends on the arrangement; hiring a payroll service provider generally does not remove the employer’s federal employment-tax obligations. The handoff steps above are Runbook’s operating recommendations, not an IRS-prescribed transfer procedure.