Females lack the black belly and flanks.
Nomenclature is extremely confusing. This species was formerly known as Black-faced Waxbill. However there is another similar bird that used to be called Black-cheeked Waxbill (Estrilda charmosyna). Its English name was changed to Red-rumped Waxbill by Sibley & Monroe & Clements (but see below). It lacks black on the throat. HBW and the "Finches & Sparrows" book by Clement et al lump both these species under the names Black-faced Waxbill and Black-cheeked Waxbill respectively.
For consistency, I have followed Clements with regard to English names, but I personally disagree with their choices in this case. Clements adopted the current names in their 4th edition following Sibley and Monroe. However IOC, African Bird Club, and HBW retained the old names for these species leading to considerable confusion. Using the same English name for two different species cannot be a good idea. E.g. looking at eBird records for Black-cheeked Waxbill shows numerous records for places like Samburu, Kenya where I think Red-rumped Waxbill would be more expected.
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