Hi,

The Countif sets up an array of 1s or 0s for where the values in all the cells above the current formula exist in the whole of column D. Where ther is a first occurrence of the column d cell there will always be a zero in the array and hence the MATCH with zero will return the row number in column D where that value is found an then Index uses that row number.

Where there is a duplicate the countif array will contain all 1s, and hence a Match for the value 0 will return an error and hence a blank

However since you have 365 a better formula would be

which will then Spill the fomula automatically as far as required to list the unique values.

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