Your calculations are correct. However, your parenthetical is incorrect as written: you’re not comparing the depreciation amount ($570) to the salvage; you’re comparing the residual ($855 = $1,426 - $570 (with rounding)) to the salvage.

The residual value isn’t subtracted anywhere. In straight line depreciation it isn’t needed, as the calculation ensures that you won’t depreciate past the salvage value; in double-declining balance it isn’t used in the calculation, so you need to compare it to the salvage each time to ensure that you don’t depreciate past the salvage value.

By the way, you can check your calculations easily in Excel using the depreciation functions SLN and DDB.

Thank you, that makes sense. Would you recommend using the financial calculator for this or is it easier to work it out in theory? I know how to calculate SL on BA II Plus, but is there a way of calculating DDB?