The phrase "allowed to supplement" is correct and usable in written English.
It can be used when discussing permissions or rights to add additional information or materials to something.
Example: "Participants are allowed to supplement their presentations with visual aids to enhance understanding."
Alternatives: "permitted to add" or "authorized to include".
Counties are allowed to supplement the state minimum, but that doesn't affect state lawmakers' pensions.
Under the bizarre system that governs Albany, politicians are allowed to supplement their modest salaries with outside employment.
Furthermore, though institutions are allowed to supplement your NRSA stipend (as long as you continue to work at least full-time on your training project), they are not allowed to supplement your stipend using DHHS Department of Health and Human Servicess) funds.
In this study, individuals with severe, treatment resistant pain were allowed to supplement their only partially effective opiate pain medications with marijuana.
Participants were also allowed to supplement the diet provided with tea, coffee, juices, carbonated drinks, spreads, margarine and oils in cooking.
Each asylum seeker in Britain gets a meagre £36.95 to live on (and they are not usually allowed to work to supplement this sum).
So wouldn't a solution consistent with that argument be that the other women should be allowed to take supplements — not that Semenya should take inhibitors?
The master's program allowed her to supplement her income by working as a graduate teaching assistant.
Though the craftsmanship is evident – in the delicacy of the pair of seasonal ballads June Hymn and January Hymn, in the hillbilly-ballad-cum-indierocker Rox in the Box – it sounds as though Meloy has allowed instinct to supplement his intellect.
At the provincial level, China's use of drones has allowed it to supplement and bolster its pollutant monitoring services and border patrol units.
At the same time, it continues to offer third party events discovery within its apps, saying the business model it started with hasn't changed but that its growing audience (and the data it's able to extract from them) has allowed it to supplement that by programming its own events.
