Microsoft Office 365 for Windows, Office 365 Pro, and Office 365 Home for Business customers can get $10 for a month free of charge.
The offer was available for new customers and existing customers on March 10 and can be activated from today, the company said.
The offer will be available until June 15, 2018.
The free offer will work for all Office 365 customers with an existing Microsoft Account.
The Office 365 Free Trial is valid for one year.
Microsoft said the offer will continue until June 16, 2018 and can only be redeemed for Office 365 Premium, Office Online, and Outlook.com subscriptions.
To activate the offer, sign in to your account on the Microsoft site and go to the Sign In tab.
After you have signed in, click the Settings button in the top right corner.
Click the Change button in that box.
Under Your Account Settings, click Additional Settings.
Select the Microsoft Account Settings tab.
In the Additional Settings section, select the Microsoft Office Online tab and enter the password for your Microsoft account.
Once the change is complete, click Continue.
If the Microsoft account is already signed in to Office 365, it will be able to activate the free offer immediately.
Microsoft has not released any information on how long this offer will last.