Contribution guidlines

Yes, per https://help.imdb.com/article/contribution/filmography-credits/cast-acting-credits-guidelines/GH3JZC74FVYKKFMD#voice: "Due to the difficulty of verifying uncredited voice involvement, we don't allow uncredited voice credits." Whereas indeed there are cases of filmography items that bear both attributes (e.g. Julianne Moore being the voice of ARIA in EagleEye), since somehow proof of participation was uncovered. Yet the IMDb staff do reserve the right to remove certain items that reflect uncredited work and retroactively revise the eligibility criteria: https://help.imdb.com/article/contribution/filmography-credits/i-worked-on-a-title-but-did-not-receive-a-screen-credit-can-it-be-listed-on-imdb/G3BDEA5Y4U9LP9BW#. As far as I know, there isn't really a strong justification for this reservation of right, but sometimes performers do come here to demand that any reference to one particular uncredited work or another be suppressed from display. At the end of the day, this is why the a number of IMDb's policies are referred to as guidelines, but IMDb is committed to making sure that credited work is never removed once it is documented in the database, and apart from verification of birth dates and death dates, most of the remaining guidelines are kind of wishywashy. I suspect that questions of high workload, if not chronic technical limitations, factors into the flexibility of (and establishment of exceptions to) some of the policies. In other words, sometimes it is just to hard to articulate a concrete guidelines that accounts for all contingencies.