Just wanted to add that when Form 3115 is filed (i.e. the change of accounting method is effected), the catch-up depreciation (prior years') is a deduction line item under "other deductions" on Sch E.  The current year depreciation is deducted on the "depreciation" expense line.  The accumulated depreciation, and thus adjusted cost basis, will then be all caught up.  

If NO Form 3115 is filed, the adjusted cost basis would still be the same - because the recaptured depreciation is the higher of the "allowable" and "allowed" amount.  Just that by filing Form 3115, the tax benefit of the "allowable" depreciation - the prior years' - can be realized in one (the filing) year, instead of being lost in the vacuum.