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Struggling with adding custom prefix in Lists that counts upwards with each entry

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Posted on by jc89

Hi,

I'm brand new to Power Automate, struggling with what I imagine is quite a basic solution regarding custom prefixes on unique IDs in Microsoft Lists.

Our company holds a spreadsheet where we pick the next number for each new project - for example latest is Q21567. We are replacing this system with Microsoft Lists and using lists to generate the next number in the sequence using a unique ID. We'd like to continue on in the same sequence to minimise any unnecessary messing around in our file server etc.

Can anyone show me step by step how I might accomplish this? It's frying my brain as a newbie.

Any help is very much appreciated.

Jonathan

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Building flows

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David_MA 12,982 Super User 2025 Season 2 on at

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SharePoint (aka Microsoft Lists) has a built-in column named ID that you can use to generate the unique IDs. The ID column in SharePoint is the primary key and always begins at 1 and can only be used one time. Once you know the last item in your existing spreadsheet, you can use an expression to increment the SharePoint ID by the last value in your Excel spreadsheet. You would use this expression based on your example above:

add(triggerOutputs()?['body/ID'],21567)

For whatever field you want to populate this into, just manually add the Q. For example:

If this ran on the item in SharePoint with the ID of 1, it would return Q21568.

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jc89 6 on at

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Hi there David_MA, thanks a lot for your help.

I did what you mentioned, and have been returned the following error message.

Would you know how I should correct this? I tried to change the variable type to string without really knowing what I'm doing but have the same issue.

If it helps, which I'm not sure it does... my test data looks like this after trying.

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jc89 6 on at

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Also my flow setup looks like this

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David_MA 12,982 Super User 2025 Season 2 on at

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What expression are you using to populate the field? It would be impossible for the ID field in the SharePoint list to be null as it is a system field and is required.

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jc89 6 on at

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I put it in exactly as you'd written it, hopefully this picture shows

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David_MA 12,982 Super User 2025 Season 2 on at

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Very odd. I duplicated what you did and do not get any errors. Is your Q Number field a string? If not, change it to a string since you are prefixing it with Q. That's the only thing I can think of at the moment unless there is some other field that you are updating with an add expression.

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