Write an organisation's name in full, and, include the abbreviation in brackets. Thereafter in your work, when you refer to the organisation, you can use the abbreviation.
How you present this depends on your academic writing style, here are some examples:
Example 1:
In this example, it is the first time writing the organisation name, followed immediately by abbreviation, in brackets (then write the abbreviation thereafter, in the rest of your work):
According to the Higher Education Policy Institute (HEPI), UK universities...etc. ...your paraphrased words would be written here, then it ends with a citation, using the BU Harvard author date method (HEPI 2020).
Or, it may be written like this...
Example 2:
In this example, the Higher Education Policy Institute is written, then abbreviated immediately afterwards, with the year of the quoted text
The Higher Education Policy Institute (HEPI 2020) proposes "quoted/copied text is inserted here".
In this case, no page numbers are included with the quote because it is taken from a webpage with no page numbers. The citation in this example is placed at the beginning, not at the end of sentence.
Or, it may be written like this...
Example 3:
You may not include the organisation name to describe who you are paraphrasing or quoting, so you may include the abbreviation in square brackets, within the round brackets, like this, for example:
"Quoted/copied text is inserted here" (The Higher Education Policy Institute [HEPI] 2020).
Abbreviating organisation names has the bonus function of helping with word count i.e. HEPI does not have to be spelled out every single time; HEPI is one word instead of four.