In not-negated English sentences with indefinite expressions following the verb, there is variation between the indefinite article and any as determiners of nouns. The standard view is that singular count nouns take the indefinite article and singular non-count and plural nouns take any. However, it is possible to encounter examples like it isn't any threat, there isn't any lock or I don't have any problem.The article studies variation between the indefinite article and any as post-verbal determiners of singular nouns in 21,084 not-negated sentences in the spoken component of The Corpus of Contemporary American English, COCA SPOK. The indefinite article is dominant with 90 per cent of the tokens. Variation is extremely rare in sentences with copular be and much more frequent in sentences with existential be and have. Among the reasons for variation between verb types is the use of do-support with have (but not with be). Expressions such as have a job/car/home or there's not a/an with uncontracted not may also prevent the use of any. Variation occurs mostly with abstract nouns such as problem, choice, way, place, reason. This finding is surprising as abstract nouns have rarely been discussed in the literature on varying countability of nouns.