I want a select statement to return two values, sum of one column and customer number

I have two columns one called invoice_number and the other invoice_amount. I want a select statement to return two columns.... invoice_number and then the sum of the invoice_amount(s) for each unique invoice number.

SELECT sum(invoice_amount) AS Totalinvoice_amount FROM InvoiceTB where invoice_number = 'INV102'

This is where I've started, which returns:
Totalinvoice_amount
500.00

Any help is appreciated.

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