Thank you for your quick and helpful response.
The questions in the pdf are very similar as you can see below.
This is the NFH question:
Can I just check, according to our records, you have in the past received [ff_bentype01 - ff_bentype41]. Are you currently receiving[ff_bentype01 - ff_bentype41]either just yourself or jointly{if HHSize > 1 & (livesp = 1 or livewith = 1)}?
This question is the same from Wave 2 up to and including Wave 9.
This is the OTHBEN question:
Are you currently receiving any of these payments ,either just yourself or jointly{if hhsize > 1 & (livesp = 1 or livewith = 1)}?
This question is the same from Wave 6 up to and including Wave 9. Between Wave 2 and Wave 5 the same question is being asked, but then in the variable BENTAX.
From the questions one would expect that there would be a considerable amount of people mentioning receiving WTC income in the NFH variable and at the same time mentioning that they are receiving it in OTHBEN (or the older BENTAX variable until Wave 5). But the opposite is true, there is no overlap, they are mutually exclusive. Because this seems so unlikely to me, I wanted to explore the difference in definition between OTHBEN and NFH further.
Could you explain why the observations are mutually exclusive, i.e. there is no one mentioning receiving Working Tax Credit in NFH who mentions receiving it in OTHBEN and vice versa? Maybe there is some obvious explanation I am missing here. Again, many thanks.
These are links to the variables concerning Working Tax Credit:
https://www.understandingsociety.ac.uk/documentation/mainstage/dataset-documentation/variable/nfh20
https://www.understandingsociety.ac.uk/documentation/mainstage/dataset-documentation/variable/othben5
https://www.understandingsociety.ac.uk/documentation/mainstage/dataset-documentation/variable/bentax1