Draft guidelines for the four main REF panels had suggested that only arts and humanities submissions would be allowed to include a back-up choice in case panellists failed to be convinced that work of "extended scale and scope" - such as a book - should be double-weighted.
This would have meant that research in other fields risked being marked down if reviewers disagreed that an "output" was worth double - as the researcher concerned would then be left with three instead of the four pieces of work needed for REF assessment.
But following concerns raised in a consultation on the panels' criteria and working methods, submissions across all disciplines will now be able to include a reserve "output".
The change is among a number of alterations made in the final panel guidelines, due to be published next week, in a bid to make the process more "consistent" across all disciplines and to reduce the burden on institutions.
Others include reducing the information required on the contributions made by co-authors, a cut in the amount of data needed on technicians and research degree students in some physical science disciplines, and a decision to include more examples of what constitutes impact in the social sciences.
The language used in the panel guidelines has also been made more similar "wherever the same meaning is intended".
"Wherever there isn't a reason to differ it's been made consistent," said Graeme Rosenberg, REF manager at the Higher Education Funding Council for England.
Publication of the final panel criteria will act as the starting gun for institutions to begin preparing their submissions ahead of the REF deadline in November 2013.
The changes follow a decision announced last year to allow women to submit one fewer output to the REF for each period of pregnancy they experience during the census period.