"To allow the deduction" means giving permission or approval to subtract or remove a certain amount of money, usually for tax purposes, from the overall total. Full definition
At the state level, many states do allow a deduction for amounts put into a 529 plan. (dinesentax.com)
As of tax year 2014, however, the tax rules only allow the deduction of medical expenses over and above 10 percent of adjusted gross income. (sapling.com)
Current laws do not allow deduction if the premium is too high in comparison to the risk cover. (business-standard.com)