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Start with the credentials, because that is the most common cause. The same KRA PIN and password that work on iTax are what eTIMS uses, so if the login is rejected, verify them on iTax before assuming the system is broken. A dormant or recently reset PIN can also block access until it is sorted at KRA.
If the credentials are right and login still fails, the portal may be slow or temporarily unreachable rather than wrong about you. Try again after a short wait, and avoid repeated rapid attempts that can lock an account. If you keep getting an error code such as 90001, that points to a PIN that is not active for eTIMS, which only KRA can resolve. Where you are set up on Veira, you issue invoices through the app rather than logging in to the KRA portal for each sale.
Related questions
What login does eTIMS use?
Does eTIMS lock after failed attempts?
Do I log in to KRA for every sale on Veira?
Veira gives Kenyan shops one calm app for selling, M-Pesa, KRA eTIMS and stock, with a free terminal. Book a demo and see it set up for your trade.