More detail
The important shift is that eTIMS is no longer only a VAT concern. KRA has widened the requirement so that businesses generally are expected to support their sales and, for income tax purposes, their purchases with electronic tax invoices.
Rather than quote a threshold that may move, the honest guidance is to check your own position with KRA or your accountant, since the requirement reaches far more businesses than the old register rules did.
Related questions
Is it only for VAT-registered businesses?
How do I know if it applies to me?
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.