Hi, 

Please refer the below app link 

 https://apps.odoo.com/apps/modules/14.0/stock_no_negative/

Hope it helps

Hi,
To prevent negative stock in odoo14, you can try using this v13 module in v14 and see whether it will get worked or not.

Module:  https://apps.odoo.com/apps/modules/13.0/stock_no_negative/

Sometimes it will get installed without any errors/issues. If there is some errors, you have to adjust the code accordingly to make it usable.

Thanks