Writers get better through practice but they are also encouraged to read as much as they can, to learn from others.
I think accountants who want to improve their writing skills should heed this advice.
Read finance reports and documents from inside and outside your organisation with a sense of curiosity. If you read something that seems to be very effective, ask yourself how does it differs from what you would write? Is the use of language or structure different? Or is the layout of the words and figures done in a way that is especially clear? Or perhaps there has been good use made of graphical features like colours and fonts?
By the same token, I suggest you do the same when you read something that is not very effective. Indeed, perhaps you could learn as much from what does not work as from what does.