Yes, it is usually intended as a monthly payment, BUT the actual UBI (in theory) doesn't (and shouldn't) pass through a "means test", i.e. (still in theory) it is "Universal" and as such all citizens should get it regardless their income or estate, as the Wikipedia article highlights:
>This article is about the system of unconditional income provided to every citizen. For the means-based model of social welfare, see Guaranteed minimum income.
Indeed. One of the main criticisms of both Canadian major experiments with UBI (Manitoba in the 70s, and Ontario in the last few years) was that while they paid regularly, both programs were relatively short-lived -- a few years. This doesn't appropriately model the incentives and behaviours people would likely engage in if they knew with reliability the program would still be paying them in ten or more years. It wouldn't capture either negatives like people leaving the workforce permanently, or positives like going back for a four year degree they couldn't otherwise afford. Participants likely treated it as a one-time windfall (if over a couple years).
>This article is about the system of unconditional income provided to every citizen. For the means-based model of social welfare, see Guaranteed minimum income.
https://en.wikipedia.org/wiki/Guaranteed_minimum_income
also sometimes called "basic income" (without the "Universal")
which is more pertinent and actually the one on which some (mostly failed) experiments have been done or are being made.