State tax filing

"SDA" may mean Special Depreciation Allowance, as it does for the IRS. You could check your state's Department of Revenue website for information.

For the Federal SDA, see this IRS article on depreciation and recapture:

(An iPhone is in the same category as a computer for this purpose)

You may be able to deduct the acquisition cost of a computer purchased for business use in several ways:

• Under Internal Revenue Code section 179, you can expense the acquisition cost of the computer if the computer is qualifying property under section 179, by electing to recover all or part of the cost up to a dollar limit, by deducting the cost in the year you place the computer in service. If there's any remaining cost, you can either depreciate it with a special depreciation allowance in the year you place the computer in service if the computer is qualified property or you can depreciate any remaining cost over a 5-year recovery period.
• The special depreciation allowance is 80% for certain qualified property acquired after September 27, 2017, and placed in service after December 31, 2022, and before January 1, 2024.
• Alternatively, you can depreciate the acquisition cost over a 5-year recovery period in the year you place the computer in service, if you don't elect to expense any of the cost under section 179, the computer isn't eligible for the 100% special depreciation allowance in the year you place the computer in service, or you decide to elect out of any special depreciation allowance for the class of property that includes computers.
• You can never deduct more than the acquisition cost.

Qualified property is: 

• Tangible property depreciated under MACRS with a recovery period of 20 years or less; 

• Computer software defined in and depreciated under section 167(f)(1); 

• Water utility property (see 25-year property, later); and 

• Qualified film, television, and live theatrical productions, as defined in sections 181(d) and (e)

See also IRS Publication 946 for more information.