You have to file IRS Form 3115 in order to correct your depreciation method. You don't have a choice here. While the TTX package does include the form, it does not offer much help, as that form can be (and usually is) complicated. Basically, since you did not depreciate for more than 2 consecutive years, you have to use form 3115 for a "change in accounting method". You should seek professional help with this... expecially if your state taxes personal income.
Per IRS Publication 946 at https://www.irs.gov/pub/irs-pdf/p946.pdf starting on page 13:
Generally, you must get IRS approval to change your
method of accounting. You must generally file Form 3115,
Publication 946 (2023) Chapter 1 Overview of Depreciation 13
Application for Change in Accounting Method, to request
a change in your method of accounting for depreciation.
The following are examples of a change in method of
accounting for depreciation.
• A change from an impermissible method of determin-
ing depreciation for depreciable property if the imper-
missible method was used in two or more consecu-
tively filed tax returns.
• A change in the treatment of an asset from nondepre-
ciable to depreciable or vice versa.
• A change in the depreciation method, period of recov-
ery, or convention of a depreciable asset.
• A change from not claiming to claiming the special de-
preciation allowance if you did not make the election
to not claim any special allowance.
• A change from claiming a 50% special depreciation al-
lowance to claiming a 100% special depreciation al-
lowance for qualified property acquired and placed in
service by you after September 27, 2017 (if you did
not make the election under section 168(k)(10) to
claim a 50% special depreciation allowance).
