Creating an Index number in DAX

[oldrunner]

Hi,
I need to create a column with index numbers by categories. I have for example 100 different customers and a total of 500 invoices. I need to have a unique index number per customer and invoice. So they count need to start with "1" per customer.

Using the index function in the power query editor doesn't work, it always returns an error.

Any help is highly apprechiated.

[oldrunner]

Thanks,
Rankx replied with an error. I struggle to concat the customer code and sales invoice code to get a unique key.

[Keith_Fernandes]

Create a calculated column on your table using concatenate dax function to create a unique key. Also what is the RANKX error you're getting?

[Keith_Fernandes]

Try to concat customer_code and Sales_invoice_code to generate a unique key. You can then create an index on this. You can also use RANKX function to get unique count against each value. Try these workarounds.