Work based Cost recognition basis question

Under the matching principle and accruals concept, we are required to recognise costs in the period in which they were incurred, and adjust where transactions have taken place and this has not been represented properly in the accounts.

Is it permissable to use the same techniques to effectively ‘change’ the basis as to which a transaction has been determined? for exampe, if a period of transactions have been invoiced based on a certain cost measurement basis, is it allowed under IFRS to them change this cost basis to another variant?

Basically, my employer is in the travel industry. Costs are either recognised on a booked date basis, so when the booking is made, or on a departure basis, when the booking actually travels. Currently, the cost basis can be either booking or departure basis, dependant on the supplier contract.

So my employer recieves 2 types of invoice, dependant on the supplier. My employers accounts are all prepared based on the departure basis, so there is a process in place which effectively adjusts the booking transations, to represent what my employer expects the departure value to be for that period. I dont think this is correct, I have been informed that it is an ‘accrual’, so its fine, but as I see it, they are manipulating the transaction to suit their reporting requirements. If audited, there would not be any supporting information to evidence the values in the P+L, only an explanation under my employers theory

I just wondered if anyone can support my suspicion, or tell me why I am incorrect?