Pay As You Earn — the income tax your employer deducts from your salary and remits to the GRA.
The order matters: SSNIT comes off your basic salary first, then PAYE is charged on what remains plus your allowances. Tax is not charged on the SSNIT contribution.
Rates are graduated. The first slice each month is tax free, and the rate climbs through bands to a top marginal rate.
If your employer computes PAYE on gross pay before deducting SSNIT, you are paying too much.