I write with some data in NFC Tag. After transmitting all the data the message to the user should be:
Data has been written
Data is written
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The first option, 'data has been written', is slightly more correct.
is Past Perfect Tense, used for a process that took time, but is now finished.
is Present Tense, used to describe the current conditions.
However, it's totally fair to say that written could be used as a verb (meaning "the computer created/sent the data") or as a noun (meaning, "the data is all in a completed state"). Grammatically, the second option is a more complicated construction, being a verb phrase, so it's very slightly less desirable.
Realistically, though, your user is probably more interested that the process of creating the data just completed rather than the process is currently complete, and has been complete for some undisclosed amount of time.
"Has been" is used to convey the present perfect progressive tense which means an on-going action that started some time ago and continued till now.
Since you are talking about NFC tag, this means that the data was getting transferred and now it is completed.
I totally agree with rsegal's paragraph that the user is more interested in the progress (or completion) of the data transfer, it'll take...
The data has been written