A U.S. tax return must be filed if a taxpayer pays income tax payments during that year or expects an income tax return. Source : Longman TOEFL PBT CD-ROM
I don't understand why we use the word or here and not the word and. I think the sentence means something like :
- The people who must fill a U.S. tax return are the ones who pay income tax payments during that year and the ones who expect an income tax return.
Which (maybe) can be omitted to :
- The people who must fill a U.S. tax return are the ones who pay income tax payments during that year and {omitted} expect an income tax return.
I also thought that all the people who can claim an income tax return must have paid the tax already that year, and so both "pays income tax payments during that year" and "expects an income tax return" describes the same taxpayer, but maybe that is not how the system works.