After posting sale invoice my cost of sale is not being effected in report

Thank you for reaching the Community, Iftikhar Azam.

May I know what report did you pull up to try and see the cost of sale? Any information or screenshot will be appreciated. 

In the meantime, you can check out this article to see different kinds of sales report: Use reports to see your sales and inventory status.

Click the Reply button to add details about your concern. I'll be in touch. Have a good one!