I am cataloging items in a spreadsheet using Google Sheets. Every item needs a unique ID, which is a sequential code formatted like ABxxxxxx, where AB000000 < ABxxxxxx < AB999999, starting from AB000001, AB000002, AB000003, etc., and counting up to AB999999.

Some items in my sheet already have unique IDs, but many do not. I am trying to find a formula that generates an ID, and checks if the ID is already in a specific column.

If the new ID is not already in the column, then that ID becomes the new, unique ID for the item; otherwise, if the ID is already in the column, generate a new sequential ID, and check again to see if that one is already in the column.

I believe that I can see if the ID is already in the column by using the '''IF''' and '''COUNTIF''' formulas, and I can check to see if a value is unique using the '''UNIQUE''' formula.

However, I cannot seem to find a formula that will generate a new, unique ID for every item in a column which doesn't already have an ID. Attached is a screenshot which hopefully can illustrate what I want my formula to do.

Is this even possible in Sheets?

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1 Answer 1


You can create the sequential IDs with this formula:


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Then, you can set a filtered range, excluding those values already existing in your range:


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And, finally you can use BYROW to state that if A column has a value, use that value and if it hasn't it scans with INDEX through that filtered range (ROW(each)-COUNTA(A2:each)-1) is used to calculate how much does it need to progress)


enter image description here

Use only the last column, it was just explaining my thinking! Possibly there are other ways to do it with SORT and MATCH

  • 1
    Great solution. Suggestion to simplify 'FILTER(ids, BYROW(ids, LAMBDA(each, ISNA(XMATCH(each, A2:A)))))' down to 'FILTER(ids, ISNA(MATCH(ids, A2:A, 0)))'
    – Blindspots
    Commented Apr 11, 2023 at 17:49
  • 1
    Thank you very much, Martín, that solved my problem!
    – Ava O.
    Commented Apr 11, 2023 at 22:04
  • I'm glad it was useful!! (and yes, @BlindSpots surely that works! I was doing something else and kept BYROW)
    – Martín
    Commented Apr 12, 2023 at 0:02

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