From this year, the so-called 'tourist house tax' of Kes. 26,000 per annum that foreign owners of property not resident in Kenya, by law, have to pay to the Tourism Regulatory Authority (TRA) in order not to incur penalties, even retroactive ones, will have to be paid online, like almost all services now, with some relative hiccups and difficulties that can however be overcome.

Here's how to do it:

First of all, some considerations: there is a form to fill out, which is inclusive of multiple situations, all entries must be filled in carefully anyway.
Reiterating that it is a renovation, that it is a freehold flat that is not rented out, fill in income or invoices, and on the company administrator page enter personal details for the umpteenth time. Remember that the tax, which at first was only meant for those who sublet their property or hosted people outside their family circle, is now a real property tax.
If someone then sublets, they have to declare income, pay licences and the various tourist taxes on hospitality.
The system still has 'bugs', according to the TRA, so for example, it now charges 27,050 instead of 26,000 shillings. But so be it.

Enter trimspublic.tourismauthority.go.ke and register.

On the home page proceed, then where it says "renewal", if it is a renewal, go in and fill out only that form, even if the site indicates more than one licence with the same number.

On the next page, where it is required to enter PIN, Title and Passport documents, enter one document at a time, in the permitted formats (including Jpg).
Each time a document is successfully entered, the upload is confirmed and the wording changes to "Review". Only then enter another document.

Then proceed with the payment, you can also use Mpesa, but there are other payment methods.
At the end of the operation, you will receive two emails.
The first receipt, the second with the certificate to be printed.

(thanks to Maurizio Gallo for his collaboration in the drafting)