How to separate a shared Google Workspace or Microsoft 365 tenant after buying a business

The short answer: settle ownership on paper, then move the data

To separate a shared Google Workspace after a business sale, agree in writing which users, domains, shared drives, groups and mailboxes belong to the company you bought, then create a new tenant under that company's billing, migrate under a transition services agreement (TSA), move the domain last and keep a report proving what moved. The same sequence works when the seller's businesses share one Microsoft 365 tenant; only the tools change.

The order matters because whoever controls the old tenant can read, retain or delete everything in it until the split is finished. Ownership goes on paper before anyone touches the data.

Why do a seller's businesses end up in one tenant?

Owners who run several companies rarely build separate IT for each one. Look for these signs during diligence:

• One primary domain, with the other companies' domains added as secondary or alias domains.
• Staff who work for two companies from one mailbox, such as a shared controller, office manager or dispatcher.
• Shared drives or SharePoint sites organized by function, such as accounting or HR, rather than by company.
• One billing account, one super admin (often the owner or an outside IT provider) and single sign-on into apps used by several businesses.
• A management company that employs the staff and charges each operating company a fee.

When a parent's IT team runs the tenant for several subsidiaries, the control-versus-ownership question is covered in holding company IT shared services.

What to have in place before migrating

• The purchase agreement schedules: asset or stock deal, whether books and records, domain names and software accounts are listed as purchased assets, and what the seller must keep confidential.
• A signed TSA for email and files: how long it runs, the seller's cooperation duties, a no-deletion commitment while it runs, cost, and who may access what.
• Company-controlled admin or export rights in the old tenant; if you do not have them yet, start with recovering admin access after an acquisition.
• A list of shared employees and which entity actually employs each one.
• Any litigation hold or retention obligation affecting either business.
• A migration partner, either your incoming IT provider or a specialist; choosing an MSP after an acquisition lists the questions to ask.

How to split the tenant, step by step

1. Inventory the whole tenant. List active and suspended users, former employees' mailboxes and archives, groups and distribution lists, shared drives or SharePoint sites, shared mailboxes, calendars, domains and aliases, and every third-party app that signs in through the tenant.
2. Sort each item as yours, theirs or mixed. The purchase agreement is the rule book. Where it is silent, agree a written allocation with the seller.
3. Stand up the new tenant. Create it under the bought company's billing, with two company-controlled super admins and multi-factor authentication from day one. Size licensing to real headcount; growing Microsoft 365 customers should read about crossing 300 users on Business Premium before choosing a plan.
4. Migrate the clean items. Move your mailboxes, drives, calendars and contacts with a migration tool, including the archives of former employees. Departed staff mailboxes often hold the oldest customer and project history the company has.
5. Split the mixed items by agreed rules. Move shared-drive folders by company. For a mailbox used across both businesses, export only the threads that match agreed filters, such as customer domains, labels or date ranges, and record the method and the seller's sign-off.
6. Repoint connected apps. Move single sign-on, e-signature, CRM, accounting and payroll integrations to the new tenant before the old accounts close.
7. Move the domain last. A domain generally has to be released from the seller's tenant before the new tenant can verify it, so plan a cutover window and update mail routing and authentication records (MX, SPF, DKIM, DMARC) with your IT provider. Check each vendor's current documentation for the exact sequence.
8. Verify and document. Compare item counts and sizes between source and destination, open a sample of the oldest files and keep the report.
9. Close out with the seller. Get written confirmation of what the seller kept, what was removed from the old tenant and the date TSA access ended.

Who owns the records in a mixed tenant?

The purchase agreement decides what transferred; copyright law helps decide who owned it in the first place. Under the Copyright Act's definition of a work made for hire, material an employee prepares within the scope of employment is treated as the employer's work. In owner groups, that employer may be a management company or the seller's other business rather than the company you bought.

So documents a shared controller wrote for your company may belong to another entity unless the purchase agreement or a written assignment moved them. Ask counsel to check before you treat mixed records as yours. This is general information, not legal, tax or financial advice. Confirm with your own counsel before acting.

Why mixed records complicate a later SourceX license

Any license through SourceX starts with a clean answer to one question: whose records are these? Data that belongs to someone else, such as the seller's other business, cannot be licensed without that owner's consent, and AI buyers review a defined dataset. A tenant that still holds another company's mail makes the data inventory slower and the licensable scope narrower.

Separating now keeps the option open. A company that later meets the who qualifies baseline (US-based, 50+ full-time employees at peak (contractors excluded), a multi-year operating history on record, clear title to its own data and an executive who can sign) can describe its own systems and years of history without carving out anyone else's. The company keeps ownership under any license, and nothing is binding until it agrees price and terms and signs.

Common mistakes when separating a shared tenant

Illustrative example: a staffing agency carved out of a shared tenant

Illustrative and fictional: a buyer acquires a 110-person regional staffing agency in an asset purchase, while the seller keeps a smaller payroll services company. Both ran on one Google Workspace, with the agency's domain as the primary. The controller's mailbox served both companies, and the shared drive held both companies' client files side by side.

The buyer's TSA gave the migration team read and export rights, barred deletions and ran until a verification report was signed. Folders were split by entity, the controller's mail was exported by client domain with the seller's sign-off, and the domain moved in a weekend window at the end. Two years later, when the agency looked at licensing its placement workflow and client-support records, its inventory covered only its own tenant and its own years.

The same split comes up when co-owners part ways rather than sell; see funding a business partner buyout.

Next step

Put the tenant split into the purchase agreement and TSA before closing, not after. If you advise buyers, sellers or owner groups and see companies with deep, well-separated records, register as a partner. Owners of qualifying companies can start their own application at sourcex.si/apply.