When supplier deliveries are processed, any cost updates cause product unit prices to be recalculated.
To enable a price history to be established:
set the To Date of the existing Unit Price to the current date/time, so it is not used for subsequent charges or estimates
create a new Unit Price with:
1. a From Date the same as the previous Unit Price's To Date.
2. the same Markup and Max Discount as the previous Unit Price