NEFT, RTGS, IMPS and UPI: what is the difference?
Four names, four different jobs, and one of them is not a payment system at all.
Four rails, four clocks. The rail you use decides when the other side sees the money.
Why four systems and not one
Every one of them was built to solve a problem the previous one could not, and none of them was retired, because banking systems accumulate rather than replace.
NEFT is the oldest of the four in everyday use. It moves money in scheduled batches rather than individually, which makes it cheap and reliable and means your transfer waits for the next departure. It now runs around the clock, but the batch logic remains: your payment travels with a great many others.
RTGS exists for large amounts, with a minimum of two lakh rupees. Real time gross settlement means each transaction settles individually and irrevocably, rather than being netted against others. That is expensive to operate and exactly what you want when the amount is large enough that waiting is a risk.
IMPS was built for instant, around-the-clock retail transfers, and it was genuinely revolutionary when it arrived, because until then instant meant nothing outside banking hours.
UPI is not a rail in the same sense. It is a layer that sits on top of your bank account and lets any app initiate a payment, mostly settling over IMPS underneath. This is the source of most confusion: UPI is the interface and the rulebook, not the plumbing.
Which one you are actually using, right now
Sending five thousand rupees to a friend: UPI, instantly, free. Paying a vendor three lakh rupees: RTGS, real time, irreversible, with a fee. Setting up salary payments for two hundred employees: NEFT, in a batch, cheaply.
Your bank frequently makes this choice for you without saying so, which is why the same transfer can arrive in four seconds one day and forty minutes the next.
Four roads to the same city. One is a motorway with a toll for heavy vehicles, one is a bus that leaves on a timetable, one is a taxi available at any hour, and one is the app you use to summon whichever of them fits.
Where you meet it
Every domestic transfer you make. The next time an app offers you "instant" versus "standard" transfer, it is choosing between these rails, and the fee difference is the cost of the faster one.