Excuse my ignorance but........

[bugsy]

......why do teams sometimes refuse to disclose the transfer fee?

[Edwatch_Winston_Malone]

......why do teams sometimes refuse to disclose the transfer fee?

One of the factors is that with all of the various clauses it is hard to determine exactly what it is.  Another issue is that the fee is paid in installments and to announce the fee gives the impression that the selling club is now loaded, which raises the expectations of their supporters

[Mr_Moon]

It also benefits the buying club to not reveal the transfer figure as it brings unnecessary attention and pressure on the manager and player if he didn't perform.

The majority of clubs are privately owned so don't have to make their transactions public.

[The King]

They aren't required to disclose them. One might even ask why they keep doing it.

[BishopsParkFantastic]

It all gets revealed eventually in the clubs annual accounts - which are available for public scrutiny.

[Quills]

They're also commercial entities at the end of the day, no reason to publicise your dealings to your competitors if you don't have to.  I'm amazed that so many details are in fact public (which is why it's always worth taking the quoted figures with a pinch of salt).

[DukeTyrion]

They aren't required to disclose them. One might even ask why they keep doing it.

Because some of the clubs involved are PLC's and therefore have to disclose it.