Please can someone answer me why my invoice said paid when I sent it out?

Hello Mopanddust-hotma, 

Welcome to the Community page, 

You more than likely  have automatic pay turned on in the settings, to check and to turn it off, if you go to the main cog wheel>account and settings> advanced > automation>  automatically apply bill payments> toggle this off> save> done.  This will then stop it from happening next time for you.