Need to Relate 2 tables and get result by criteria

[ronydsouza27]

Table A					Table B
Date	Invoice No	Amount			Date	Invoice No	VaT Amount
01-06-2021​	DXB-123	100​			01-06-2021​	DXB-123	10​
01-06-2021​	DXB-124	200​			01-06-2021​	DXB-123	5​
02-06-2021​	DXB-124	300​			02-06-2021​	DXB-124	300​

Note need to get a additional column in table A Vat amount the result has to be

for the first line 15 ( it will add up 5+10)

Secondly the in both the tables Invoice no. are not unique value .

Need to know the DAX formula

and how can I derive the answer

 

[AlanSidman]

If the invoice numbers are not unique, should the invoices be grouped on the date? What unique value should be used for grouping?