I'm an existing Office 365 subscriber.You can choose to pay for your subscription on a monthly or yearly basis, and the Microsoft 365 Family plan lets you share your subscription with your family for up to 6 people, and use your apps on multiple PCs, Macs, tablets, and phones. With a subscription, you'll always have the latest features, fixes, and security updates along with ongoing tech support at no extra cost. You also get extra online storage and cloud-connected features that let you collaborate on files in real time. Microsoft 365 includes the robust Office desktop apps that you’re familiar with, like Word, PowerPoint, and Excel. Microsoft 365 is a subscription that includes the most collaborative, up-to-date features in one seamless, integrated experience. However, there are no upgrade options, which means if you plan to upgrade to the next major release, you'll have to buy it at full price. One-time purchases are available for both PCs and Macs.
Office 2021 is sold as a one-time purchase, which means you pay a single, up-front cost to get Office apps for one computer.
