3.5 How to write numbers, refer to a time and to a date
If a transaction involves many figures (amounts, units of measurement, specifications), collect them in a single spreadsheet and double check whether they are correct. If numbers are likely to change, or if they are not for everyone’s eyes, keep them out of the initial drafts of your document.
There are a number of best practices, for which official national or EU legislation style guides, authoritative newspapers’ style guides may serve as a good basis.