The most appropriate way to abbreviate the name of the United Kingdom is R. U. and not UKwhich is borrowed from English.
In the news about this country, it is not uncommon to see the English form used: “Zelenski asks the UK to send fighters”, “Travelers from the UK will have to apply for a permit in their country” or “Sunak promises to lower the inflation in the UK by half.
UK is the initials of the English name of the country, United Kingdombut In Spanish, its settled name is United Kingdomfrom which the abbreviation is derived R. U.written with periods and a space. As indicated in the account of RAE Twitterthis is the spelling usually used and the advisable one, in accordance with the fact that it is usually read developed and not spelled, although he points out that the acronym RU is correctly formed. Instead, yes it is orthographically inappropriate to leave the points and omit the space: R.U.
Although in headlines and labels the abbreviation is usefulit is worth considering whether, outside of contexts where it is necessary to save space, not it would be preferable to give the full name. In any case, it is remembered that when mentioning this country, the usual thing is to put the article before: the United Kingdom, he R. U.
For this reason, in the previous examples one could have written, for example, “Zelenski requests in R. U. sending fighters”, “Travelers from the United Kingdom will have to apply for a permit in their country” and “Sunak promises to lower inflation in the R. U. to the half”.