From Longman Dictionary of Contemporary Englishon the never-neveron the never-neverBritish English old-fashioned informalBBTBFL if you buy something on the never-never, you buy it by making small regular payments over a long period SYN on hire purchase → never-never
Examples from the Corpus
on the never-never• From thence he progressed into Formula Ford, with an Alexis that he bought on the never-never.• They just let you go on buying on the never-never. 