CAP (TRADING LOSSES)

Sir i just want to confirm that,
Can we apply cap only in Current year?

for example
for a loss in tax year 2014-2015

we can use cap in only 2014-2015
remaining loss will be settled against previous year or future year profits in full amount till profit is nil.

and
by using cap we can only secure our Personal Allowance of current year
not preceding or future