How to Update price period in Price Management?

Once you have set up a price in the Price Management for any of the price types (Generic, Vendors, Offer(s)), these entries (lines with the information) cannot be deleted from the Price Management page. However, existing price settings can be modified. This option is available only for Seller's user with Seller admin rights. 

Go to Catalog → Customer Prices:

As an example, we will apply new price settings for "Microsoft 365 A3 for students Offer" that already has an existing price setting with 0% Markup (as this entry is listed in the Price Management page):

1. Select "Microsoft 365 A3 for students Offer" from the list → change Price Markup to 5% → "Save".
Note! Offer names (1) cannot be changed.   

2. When markup is updated, you can see that now Seller price is increased. The vendor price (2) will not change. 

In the picture below, you can see listed:
a. price changes for all offers of a selected Vendor.
b. Generic price changes
c. price changes of all separate Offers.
In more details read Customer Prices (Price Management).

 In more detail read the article How to adjust Markup for Offer groups?