Creating form - Mandatory Response

Hello everyone,
I started to create forms on KoBo and got stuck with a problem concerning the mandatory response.
I would like to make
that one question out of two is mandatory to be answered
2. question is only showing up if the first question is a default.

I tried different things but didnt work and also not finding any helpful hinds in the Navigation.

Hi @h_kriedemann,

Welcome to the community! You could control this with the Custom Logic feature that is within the Mandatory Response as discussed in our previous post:

Have a great day!

ok, thanks a lot for the quick response.
How do I express the custom logic if I wanna say: only mandatory if question 1 is default/not answered?
Sorry, I am not very experienced in the informatic field.

Thanks a lot in advance.

Hi @h_kriedemann
In this situation, all you need is a skip logic. I suggest you look at our article here and get a better understanding of how to apply “skip logic”.


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thanks @stephanealoo for your answer. I am familiar with the skip logic - I can use it for conncecting the two questions, but not with defining the option which makes a question mandatory or not.
My problem is that I dont know how to fill the part at custom logic (“only mandatory if…”)
Ca you help?

Greeting, Helene

Hi Helene,
Your statement contradicts itself. In summary you cannot make a question mandatory on only some instances. Unfortunately that is not supported.


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oh, what a pity. So I can not say that either on or an other question has to be answered mandatory? I thought this is what the custom logic is for?

You can allow the question to be open such that an answer is provided or not provided by setting the required=false. An alternative approach is to create two different questions e.g.

  • OptionalQuestion1 which is mandatory and thus a skip logic would lead the person to it.
  • Optional Question2 which is not mandatory and thus a skip logic would lead the person to it.

You can always merge the answer from these two questions later on.


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hi @stephanealoo,
to go more into details:
My question 1 is answered by a barcode. In case the barcode has not been able to be scanned (damage, lost, other problems) i would like to put skip logic to questions 2: identifying yourself by number-code.
If I set Q1 as mandatory and it is not answered coz of a scanning problem the form will not be complete, if i dont put the barcode as mandatory I risk to have incomplete data.
Do you understand my problem now? Any ideas?

You can operationalize this as follows

  1. Question 1: Barcode and it is not compulsory
  2. Question 2: Identify your self using a number code. This can be put such that it only appears when the barcode question is blank. Using skip logic and as such not a relevant field as you had hinted.


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thanks @stephanealoo, this is already a start, I tried that.
The problem is still:

It could be possible that neither question 1 nor question 2 is filled in and at the end the form will be declared as complete but no identification was taking place (coz neither Q1 nor Q2 have been mandatory)

Did you try to set the conditions as below

The form is as below

And you can use the attached excel.

Barcodetest.xlsx (9.2 KB)


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yes, I did it exactly that way.

But still doesnt solve the problem with mandatory-condition

I think your query is no longer clear. Unless you provide more information with screenshots, unfortunately this is the most I can be able to provide a workaround on your form. It seems what you are asking for does not necessarily fit the structure of the forms in design or application.


ok, following your advice I made a screenshot of my forms.

Short explanaition:
the forms are about identification. Basically every person should scan a barcode be identified. But I would like to put an alternative in case the barcode doesnt work or is damaged and is not able to be scanned.
So Q1: Barcode
Q2: number, only appears if Q1 is not answered (via skip logic). So far everything is fine.
Problem: I need any kind of identifcation as mandatory, if nojt the whole process/the other forms are useless. If i put Q1 mandatory and it is the rare case that barcode is not readable the form can not be completed. If I dont put Q1 mandatory I risk of getting forms which are missing important data.

I would strongly suggest you try running the form I sent you earlier and see if it works for you. The form I designed is actually meant to answer your question as you explain. Try deploying that form and testing using collect application and see if it does not sort you out.

Your logic can be summarized as Q2 will only appear when Q1 has failed. So it means either Q1 or Q2 can be answered but priority should be to Q1 over Q2.


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