For most taxpayers, the maximum pension contribution is £40,000 each tax year, although this depends on earnings. Click here to check if you are caught by the Tapered Pensions Tax. This limit covers contributions by both the individual and their employer.
Unused pension contribution allowance can be carried forward for 3 years and used as a relief for the current year. If the relief is not carried forward within three years it will lapse.
Hence the unused pension allowance for 2015/16 will lapse on 5 April 2019 if unused.