1. Bill management, accounts payable for real. You can enter vendor bills as they come in, track what's due and when, and pay a batch of them at once through Pay Bills. Simple Start has no equivalent; a business on that tier tracks what it owes vendors outside QuickBooks entirely.
2. Time tracking tied to billing. Log hours for employees or contractors against a specific customer or job, then pull those hours straight onto an invoice instead of re-typing them from a separate timesheet.
3. A third user seat. Essentials supports up to three simultaneous logins plus your accountant, versus Simple Start's single user. That's usually enough for a small team where more than one person touches the books, without yet needing Plus's five.
4. Everything Simple Start already had. Invoicing, expense tracking, mileage, receipt capture, and the standard report set all carry over unchanged; Essentials is additive, not a different product.
5. What's still missing, inventory and project tracking. There's no inventory quantity tracking and no dedicated project profitability view. Both of those wait for the next tier up, Plus.