STK Push
Also known as: SIM Toolkit Push, M-PESA Express, Lipa na M-PESA Online, STK
Full definition
STK Push is the request-to-pay API exposed by Safaricom's Daraja developer platform. Instead of typing the paybill, account number and amount by hand, the merchant server sends a signed request to Daraja specifying the customer's MSISDN, the paybill or till, the account (if paybill) and the amount. Safaricom then triggers a native SIM Toolkit prompt on the customer's phone showing the merchant name, the amount and the account, and the customer just confirms with their M-PESA PIN.
STK Push is what powers the Pay with M-PESA button on every serious Kenyan e-commerce checkout, on the Safaricom OneApp, on betting operator deposits, on ride-hailing apps, and on the growing set of subscription billers. It reduces mispayments (the customer cannot mistype the paybill), it reduces reconciliation work (the transaction reference maps 1:1 to the merchant's order ID), and it removes friction at checkout.
Safaricom's public STK Push endpoint is documented at developer.safaricom.co.ke. STK Push settles into the same paybill or till the merchant configured; the fee schedule is the standard C2B tariff.
Worked example
A shopper clicks Pay with M-PESA on an e-commerce site for KES 1,500. The site posts an STK Push request to Daraja with the shopper's MSISDN. A minute later the shopper's phone rings with an M-PESA dialog: Pay KSh 1,500 to Merchant X? PIN. She types her PIN, the site's webhook fires, order is confirmed.
Verified 2026-09-01. Definitions on paybillke are sourced from Safaricom PLC Annual Report FY2026, the Central Bank of Kenya, the Communications Authority of Kenya, the Kenya Revenue Authority, and the primary operator documentation for each product. How we verify. Report a change.