Once the assets are put to use in earlier years and form part of block of assets, depreciation can be claimed on the same in subsequent years even if all the items in block are not used simultaneously:

Once the assets have been put to use in earlier years, such assets form part of block of assets and depreciation thereon has been allowed in the past, then depreciation on the said assets can’t be restricted or disallowed in subsequent years on the pretext that only a portion thereof has been put to use. Items falling within the block of assets cannot be segregated for the purpose of granting or restricting depreciation. Once the assets are used for business, it is not necessary that all the items falling within the concerned block have to be simultaneously used for being entitled to depreciation.

[S.K.PATEL FAMILY TRUST - TAX APPEAL No.84 of 2000 - GHC]