HMOs are the operators of the scheme in Nigeria.
Just like nobody can walk into NCC to buy a Sim card, but it’s activities are an oversight on MTN, 9mobile Glo etc. Likewise, the NHIS oversees the activities of HMOs.
HMOs are the go between the end users and the hospitals.
They make monthly or quarterly payments of a standard amount per individual to HCF “health care facility”, they attend to claims for payment from these HCFs and generally try to make the scheme seamless in use