## Explanation

This formula uses COUNTIF with an expanding range to first check if the current row is the first occurrence of a given invoice number:

```
COUNTIF($B$5:B5,B5)=1
```

This expression only returns TRUE when this is the first occurrence of a given invoice number. If so, a SUMIF calculation is run:

```
SUMIF($B:$B,B5,$D:$D)
```

Here, SUMIF generates a total sum by invoice number, using the amounts in column D. If the count is not 1, the formula simply returns an empty string ("")

## Related formulas

### Sum if multiple criteria

### Subtotal invoices by age

### Subtotal by color

## Related functions

### SUMIF Function

The Excel SUMIF function returns the sum of cells that meet a single condition. Criteria can be applied to dates, numbers, and text. The SUMIF function supports logical operators (>,<,<>,=) and wildcards (*,?) for partial matching....

### COUNTIF Function

The Excel COUNTIF function returns the count of cells in a range that meet a single condition. The generic syntax is COUNTIF(range, criteria), where "range" contains the cells to count, and "criteria" is a condition that must be true for a cell to be counted. COUNTIF can be used to count cells...