Capital gain on "My Portfolio" view is incorrect

I have two ETF’s that basically track the ASX200 and ASX300 ie. A200 and VAS. Every now and then I purchase more of them or sell some. So I have multiple parcels of them with various purchase prices.

For the sake of explaining this error I will simplify the reality here so it makes the error more obvious. When it comes to capital gains tax calculations assuming I decided to use FIFO (and actually I’d prefer specific identification but I digress) then the oldest shares often have a different price than my average price per share. So when I sell shares with a higher price than the average price the reallised capital gain is less than if I sold more recent shares. So according to my spreadsheet the remaining shares in my portfolio have a higher unrealised capital gain than what sharesight shows in the “My Portfolio” view. For example, my spreadsheet shows a $44k gain and sharesight shows a $35k gain. So that is a material error.

Obviously the realised capital gains report has to know what shares are sold against which parcels to calculate a correct capital gain for tax purposes however the reporting on the front screen of my Portfolio also needs to remember which actual parcels have been sold to calculate its capital gain accurately as well.

Sharesight uses two types of calculation to calculate capital gains: Average method for Performance and FIFO (by default) for Tax.

Capital gains figure in CGT report, Unrealised CGT follows FIFO method. As they are for tax. Everything else i.e Overview, Performance Report, Sold Securities Report etc use Average method.

You will see discrepancy when you have multiple buys and partial selling.

Sure but given ETF investments in the same ETFs including dividend reinvestment schemes do that as a matter of course the report will always be incorrect with a material error. Clearly the brain of an accountant (like mine) vs a software devloper different. If it wasn’t for the cost base adjustments for capital gains tax that this product offers I’d want a refund because it’s just plain wrong. Not sure why we can’t write our sales allocations to a table and you can join that table with our holdings to create a correct report. I could certainly write it in a rapid application development environment using VBA, SQL and ADO etc.