Property CGT losses carried forward after subsequent sale

[twokcc]

How are CGT losses (from property sale) carried forward when subsequent sale made.
The gain on the subsequent sale less than the annual CGT allowance
For example
CGT loss brought forward say £20k
Gain on sale of subsequent property £5k (so less than CGT allowance for the tax year s no CGT due

Is loss carried forward £20k or £15k
Tried googling -think may be £20k but need to make sure , thanks

[Alpinestars]

£20k.

[twokcc]

Thanks Alpinestars