What's new in version 4.0

Users can now output list style API calls as simple downloaded CSV files
1. See example at the bottom of this activities page Activity List( Work item: 8203)
Reducing the number of records returned by a call to the Calendar's estimates/requisitions lists
1. Work item: 15751
Create new DV API output format that is usable by external tools (eg: PowerBI) - style=data option
1. Work item: 8485 (was released in late 3.9 API)
Projects API Projects API
1. Previously undocumented API. Includes CRUD (Work item: 19435)
Campaigns API Campaigns API
1. Previously undocumented API. Includes CRUD (Work item: 19435)
Estimated units Estimated units
Update the number of units of time estimate (work item: 19756)

Late additions

These minor items were added post release of API version 4.0

(Note: The user should pass version=5 to access these late additions)

Stages
Example added - how to allocate a purchase to a stage (using create endpoint) Purchasing API
DRA Departmental Revenue Analysis DRA API
Department field added to the following list (details) outputs (Work item: 18735):

Suppliers, Purchases, Time estimates, Expense lines (from expense sheet API), Timesheets,

CRUD for Suppliers, Purchases & expense lines also now support department field
Job/Opp notes field in job API Job Details

"jobLeadSalesNotes": "Sales notes",
New business support for job API (Work item: 20029)

New business fields exposed to API and supported in CRUD