if you were allowed say $10,000 of 179 but elected to take only $5,000. you CANNOT take the balance in the future. a 179 carryover only occurs when you elect to take more in 179 then the net business income before the 179 deduction.
if you selected to take the full $10K as per the previous example and you net business income before the 179 deduction was $8K your allowed $8K in 179 for the year reducing business income to zero. the remainder is carried over to the next year again subject to the net business income limitation.
