to decrease/to be decreased

Our company's net loss will have to decrease by double digits in order to remain competitive.

My friend said 'decrease' is correct. Shouldn't it be 'to be decreased'?
'will have to decrease' sounds strange to me. Is it only me thinking like that?

You are right. The right option is 'to be decreased' because this is a passive sentence where there is no agent. 'Will have to decrease' is an active verb phrase which requires an agent (i.e. you need to specify who has to decrease the amount spent).

To my ears, 'will have to be decreased' sounds even stranger than 'will have to decrease'. I would look for some other way of saying it.

And although the verb 'decrease' exists, it is somewhat formal and academic. You might use it in a technical paper but not in ordinary dialogue.

How about using 'reduce' instead?

'Our company's net loss will have to be reduced by double digits in order to remain competitive.'