Stuck at 305 corporation limit

I thought I had read that enterprises we're limited to 700 or 750. I currently have just over 300 corporations, but get an error message telling me that I have too many corporations when I try to buy/build new ones.

I am able to get over 300 no problem. Curious, are you a free player or paying member. Maybe free players are limited to 300? I'm not sure.

I'm a free player. I suppose that could be the case, but I couldn't find any documentation or mention of 300 being a limit.

I would like to know for sure if that's the reason.