How to amend invoice

Ramachandran R (117 Points)

15 June 2019  

Hi, 

I've wrongly invoiced customer and had put more tax during may month. Im yet to file for May month. can I amend bill and adjust tax amount in May month filing or should I adjust tax amount in June Filing only. 

Also one of my customer closed business and didnt pay the amount. How to claim the tax paid for that bill. Should take as sales return?