If you are paid in full for a sales order in one month, but do not ship it until another month, in which month do you account for the sale income?

If you are paid in full for a sales order in one month, but do not ship it until another month, in which month do you account for the sale income?
Hi... sales should be taken in only when the goods are shipped, or in accordance to your matching principle, when expenses are incurred to carry out the sales.

Prepaid sales should be taken into your financials as a liability, under sales in advance.
DR cash (B/S)
CR sales in advance (B/S)

When sales is to be recognised, reverse the advance to sales by...
DR sales in advance (B/S)
CR sales income (P/L)