Sum function with a filter is not working in a simple table

Sorry, forgot you already had added the index. 

The reason it looks unsorted, is that when you add Date, Client and Code Project, your table gets sorted by Date, Client and Code Project, in that order. If you add index to your table visual, between Code project and Vente, you will see that the index is not displayed in strict ascending order. The column you created is based on strict ascending index. And unless you include the index in your table and sort by the index, the cumulative values will appear somewhat unsorted.

And you can't really solve this by using a measure either. If you don't want to add the index in your visual, you will have to do some work in Power Query/Edit queries. The reason for this is that in Power Query it is only possible to sort by a single column at a time, if you filter by a second column, it will forget the earlier sorting. So you need to get a bit creative with various indexes: https://community.powerbi.com/t5/Community-Blog/Using-EARLIER-with-a-SMART-INDEX/ba-p/809341.

If your data resides in a database, it will be easier to modify your queries.