怎样理解"费用是已耗成本".当本期发生大额广告费,而费用有没有支付给广告公司,这时并没有发生成本耗费啊.

权责发生制
并不是说没付钱就是没发生这项费用.
其实像这些你看书的时候不理解的问题,都可以联系下会计一般原则,基本都可以解决.

Assume Ad expense = $1000
set up as
Dr Ad Expense 1000
Cr A/P 1000
when you paid it, then
Dr A/P 1000
Cr Cash/bank 1000

If the Ad was paid for two years,
then set it up as prepaid expense
Dr Ad Expense 500
Dr Prepaid 500
Cr A/P 1000

借:营业费用不着--广告费
贷:应付账款--X方告公司