The Australian Style Guide | Your definitive reference on writing style

Square brackets allow you to clarify text or mark an error. You can also pair them with round brackets (parentheses) when you need brackets within brackets in text or equations.

Body text

Insert editorial comments, particularly in quotes

The contract says, ‘The lessee has 1 buisness [sic] day to comply’.

Square brackets let you add editorial comments, particularly in quotes. Common uses include clarifying the content or noting an error (usually in spelling or grammar):

Use	Example
Clarification	The manager promised to double-check them [the figures].
Error	In an open letter to the minister, the peak body called for ‘a coordinated response to support regional producer [sic]’.

Take care where you use [sic] as it can look snarky and critical. Unless it is crucial to keep the text verbatim, you may be able to quietly correct an error. Alternatively, you might be able to ‘merge’ the editorial correction with the quoted text so it flows more easily.

Use	Example
Clarification	The manager promised to double-check [the figures].
Error	In an open letter to the minister, the peak body called for ‘a coordinated response to support regional producer[s]’.

You can also use square brackets when you need brackets within brackets. In this case, order your brackets like this: [ ( ) ]. But consider rewriting the text instead to avoid needless complexity.

This is a criminal offence [see section 2(a) of the Act].

Equations

Clarify complex equations that use multiple sets of round brackets

y = [(66 – 4) x (6 + 1) x 43]

Round brackets are common in equations as they help to show the order of operations. If an equation is very complex with multiple sets of round brackets, you can clarify it with square brackets.

[(7 + 3) x (4 – 1)] + (5 x 2) = 40

Surrounding punctuation

Place commas and full stops carefully

Never place a comma before a set of brackets, because it’s unnecessary. As with round brackets, you can put one after the closing bracket, if the following text is an independent clause. But if the bracketed text is inserted into a single clause, do not add any commas.

The contractor has reported a conflict of interest [please refer to clause 7.1(b) of the contract].

The ward nurse said the next incident [the second incident] caused even greater concern.

The ward nurse reported that incident immediately [the second incident], but again the duty manager took no action.

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Square brackets [ ]