Generally, if you have an allowable expense deduction, you should take the deduction. Here is an IRS reference. Specifically, this is related to showing an increased self-employment income in order to maximize the earned income tax credit (EITC) and/or social security benefits.
"A self-employed individual is required to report all income and deduct all expenses. Revenue Ruling 56-407, 1956-2 C.B. 564, deals with the issue of taxpayers not taking all allowable deductions in computing net earnings from self-employment for self-employment tax purposes. Rev. Rul. 56-407 held that under §1402(a), every taxpayer (with the exception of certain farm operators) must claim all allowable deductions in computing net earnings from self-employment for self-employment tax purposes.
Net earnings from self-employment are included in earned income for EITC purposes. It is defined by cross-reference to the definition of net-earnings from self-employment under I.R.C. §1402(a). This ruling applies equally to the EITC."