A form asks for an exact number. The user does not have it yet. The field is required, so they enter 0.
The product has an answer now. It just is not true.
Blank does not explain itself
An empty field can mean nobody asked, the answer has not arrived, the question does not apply, or the value is zero.
Those meanings should not collapse into one. A report may count an unknown value as zero. A teammate may read an empty field as unfinished work. The uncertainty travels farther than the form.
Let people answer honestly
"Not known yet" and "Not applicable" are different answers.
A budget can be zero because no money was allocated, or unknown because approval is pending. A delivery date can be unconfirmed without being missed.
Not every field needs a list of exceptions. But when the difference affects what happens next, the form should let the user say what they actually know.
Leave room to return
Unknown should not become a permanent hiding place. Show it where the missing fact matters, and make it easy to update when the answer arrives.
If the product cannot continue without that answer, explain why and let the user keep the work already done.
A required field should protect the task. It should not turn uncertainty into bad data.
The point of a form is not to fill every box. It is to leave the next person with something they can trust.