Comment by ojbyrne

I haven't looked at the tax rule in detail, but it looks like the "half year convention" for amortization applies.

The "half year convention" means that when you amortize a purchase, it's assumed you purchased it exactly halfway through the year, so you can only deduct half the amortization in the first year that you would normally (and the other half is in the year after the depreciation period).

So it looks like

year 1: 1/10

year 2: 1/5 + 1/10

year 3: 1/5 + 1/5 + 1/10

year 4: 1/5 + 1/5 + 1/5 + 1/10

year 5: 1/5 + 1/5 + 1/5 + 1/5 + 1/10

year 6: 1/5 + 1/5 + 1/5 + 1/5 + 1/5 (the last 1/5 being the other half from year 1 and the 1/10 from year 6).