Tier 1 general extension - income question for self employe

Hi asking on behalf of friend.

For tier 1 general visa extension for a existing tier 1 general holders, minimum income of £20,000 is required for points. For someone who is self employed is this gross income or net income after adjusting for any loss? Would appreciate if someone can kindly point out any reference to official documents.

Thanks
X

See 92.

I hope he is aware that no further extension are possible under Tier 1 (General).
The only way forward is either ILR or switching to another category he/she may qualify for.