Folks,
I always get a bit warmed up by these sorts of questions - particularly after a red wine or two. Not because you did ask the question - that is quite proper - but because you felt the need to ask! That means to me that your flight operations management is failing in its duty to you to fully inform you of how they meet their obligations as an AOC holder and as your employer.
Acceleration altitude is something of a tribal secret but should never be so.
Certification requires that the aircraft can complete a flat earth acceleration 400' after take-off at MTOM within the certified engine limits and meet all net flight path requirements. Sometimes AOC holders decide that a second segment climb to the bare minimum 400' does not provide sufficient time for crews to fully consider all of the relevant issues - that usually gives rise to a minimum company acceleration (typically 600/800/1000' dependent on aircraft type) that applies where there are no obstacle considerations. That policy may result in a commercial cost of a reduction in payload.
Where there are obstacles, the acceleration altitude is determined by the highest obstacle underlying the relevant segment, ie the 3rd or 4th or sometimes a 5th if applicable.
The actual payload that can be carried is determined by two things that are a consequence of the acceleration altitude: the engine limits for take-off power/thrust and the gradient required to get to the acceleration altitude.
You should never have to question the required acceleration altitude at any airport from which you may be required to depart - you should always know what that altitude is and you should know whether it is the minimum permitted (company or certification) or if it is an obstacle determined requirement.
If you don't know, then the person to ask is your Director Flight Operations. The answer will be one of life's lessons....
Stay Alive