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Amada0339(Enthusiast)Enthusiast
10 Apr 2025

Hello,


At the end of each financial year my index ETF issues an AMMA statement. On this statement there are AMIT cost base net amounts, one for excess (reduce cost base) and another for shortfall (increase cost base).


When it comes to selling my index ETF, do I sum up these net amounts from each year's AMMA statement to calculate my cost base for capital gains?


An overly simple example:


I held my index ETF for three financial years. It cost $250,000 to buy. The shortfall amount for the first year was $400, the second year it was $200, the third year it was $100. The excess amount for the first year was $75, the second year it was $10, the third year it was $50.


So now, my cost base is $250,565 (i.e. $250,000 + ($400 + $200 + $100) - ($75 + $10 + $50)).


Is this correct?

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7 replies
224 views
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YellowPotato(Taxicorn)Taxicorn
11 Apr 2025

Yes the total cost base would be that.


If you sell it all in one go, then you can do that.


If you have multiple purchase parcels and not selling it in one go, you would need to allocate the AMIT amounts.

Liked by Amada0339 and knaresbro
Amada0339(Enthusiast)Enthusiast
11 Apr 2025

Thank you!


And let's assume I sell the parcels at different times. How do I allocate the AMIT amounts?

YellowPotato(Taxicorn)Taxicorn
11 Apr 2025

ATO doesn't doesn't provide an example on their page.


My best guess would be to first adjust the cost base, spreading the AMIT amounts evenly into all the relevant units (units purchased or hold or had owned during that tax year). Then do CGT calculation, pairing a purchase parcel to a sell parcel.

jellycat9000(Newbie)Newbie
10 Sept 2025

Hi @YellowPotato, I'm in pretty much the same situation as @Amada0339 (bought shares in an ETF all in one go many years ago, didn't touch it, and sold all in one go last year), so thought I would ask my follow-up question here in case the answer helps someone else in the same boat.


The thing I cannot figure out is where to put that final, adjusted cost base figure ($250,565 in Amada's example) in myTax for the last FY's tax return.


The only fields I can see let me specify the following for the previous FY only:

  • The date the shares were originally purchased (2020 in my case)
  • The amount they were purchased for
  • The date they were disposed of (2025 in my case)
  • The "capital proceeds" which I assume (possibly incorrectly, but based on the help tooltip) is the total amount I sold the shares for

This means that the CGT is going to be calculated on the final sale price - initial purchase price, which I originally thought was the straightforward way it was supposed to work, until I happened to learn about cost base adjustments a few months ago.


Thanks in advance for any help. There is probably one small step I'm missing but I'm going nutty trying to figure out what it is!

YellowPotato(Taxicorn)Taxicorn
11 Sept 2025

If you need assistance, then it may be best to go to a tax agent. You should not rely on CGT record keeping tool. It's only a simplistic tool.


Cost base is not solely the purchase price. Other events can change the cost base like return of capital, AMIT, share spliting/consolidation etc

https://www.ato.gov.au/individuals-and-families/investments-and-assets/capital-gains-tax/calculating-your-cgt/cost-base-of-asset

jellycat9000(Newbie)Newbie
11 Sept 2025

@YellowPotato

Thanks for the reply!


I calculated my cost base based on your initial reply to Amada's "overly simple" example -- which just so happens to be my exact situation. i.e. adding all the shortfalls over the years, and minusing all the excesses, from the original purchase price.


Sounds like I will have to bite the bullet and go to a tax agent. I cannot find any straightforward instructions on the ATO site on how to handle this simplest of scenarios, myTax doesn't let you specify an adjusted cost base, and it sounds like the tool they give you to do this exact calculation cannot be relied on either :(


Thanks again for replying :)

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