As a general rule the management is obliged to ensure the balances are always correct. In practice the balances are confirmed mostly once a year though, and as such you want to make sure it’s as close to year end as possible.
The best option would be to confirm the balances as at year end date. This way you ensure the statements you sign off are in fact correct. If this for whatever reason is not possible – either due to very tight reporting schedule or odd end of financial year resulting in year-end closing procedures to be in a very busy season, etc. – as close as possible to the financial year end date is the second best option.
Another really good practice is to perform cycle confirmation with your biggest customers and suppliers. As real life has shown, sorting out the differences, looking for missing invoices, resending them, making sure the goods actually arrived etc. always takes much time. It takes time for both sides, results in inefficiencies and time as well as money not well spent.
So in short, make sure the date you confirm the balances, is as close to year end as practically possible and perform cycle confirmations (i.e. monthly or quarterly) with your biggest partners to ensure differences are dealt with as soon as possible and in due time rather than later.