CGT calculators and Tax harvesting montoring

Muttleythefrog

Dear all…

My wife is an investor…trading mainly shares on US market in tech and memory…. but she'll never be an administrator. So the paperwork falls to me.

She operates across T212, IG and now also IKBR.

For her tax returns 2025/6 (she started investing at start of 2026) I used cgtcalculator.com and was able to bring all her transaction data into uniformity within a master spreadsheet to get it to generate her CGT report. Paid the few hundred tax into her HMRC account she would owe from her then later completed Self assessment I filed.

I have subsequently today wondered about her ability to tax harvest so had been looking for a better calculator to use going forward for CGT calculation report and monitoring her current holdings. I found cgttracker.com.

I imported her master spreadsheet for the previous tax year after some compatibility changes and it became obvious cgtcalculator.com had made some errors in applying the necessary rules along with failing to match some tickers due to erroneous spaces in ticker name not visible in spreadsheet format. So I regenerated her CGT report and have amended her tax return so it is now correct.

Moving on. I wanted to make sure cgttracker.com would be good going forward and duly exported the csv files of transactions from her 3 platforms for this financial year to date for import. But on importing only T212 was recognised and field matched - their advertising about compatibility is completely false as clearly their software cannot identify and read data from all the main platforms. So frustrating. I have reported the problems to them.

There must be investors among you who have been around dealing with similar requirements and probably frustrations. What software do you use that is compatible with her platforms' exported data and has tax harvesting simulation to use. We're happy to pay if something will work.

Regards!

masonic

I used CGTCalculator as inspiration to build my own spreadsheet of data and then did a DIY calculation so that I could ensure it was right. I've not done a great deal of investing outside of tax wrappers though and now have all my investments wrapped.

The issue you have seems to be mainly around cleaning the source data. There are some simple things you can do to make checks easier, such as use of the UNIQUE function to throw up any variations of cell values that appear to be the same ticker.

It looks like the cgttracker.com service has been taken offline, but I suspect it will have a similar disclaimer to CGTCalculator. Likewise any other software is likely to absolve itself of responsibility for any errors, especially those caused by input data issues. If you want a capital gains calculation to be done properly and backed by professional indemnity insurance, then for a few hundred pounds you can get an accountant to do it for you.

Muttleythefrog

https://forums.moneysavingexpert.com/discussion/comment/82149966#Comment_82149966

Yeah not paying an accountant hundreds albeit you get the protection…. they'd be just as subject to error as a calculator I imagine and would they have to use one themselves. Applying the rules is not straightforward… which is why I suspect cgtcalculator fell short as an older enthusiast type bit of software.

And really wanting not to do any data manipulation for use when products out there are potentially going to be able to (and advertise they do) take source csv exports from the major platforms. Importantly my issue is that I may not be around much longer…. I need to leave my wife with something workable with simple instructions ultimately.

I wonder if cgttracker taken down after my reports of problems..It happened just minutes after.

AI has proven useful to detect errors in processing and inconsistencies in data or results…. and to such point I'm wondering if it itself can just deal with it all. It already knows how differently the platforms reports the transactions and include fees etc. It can also handle the dealing with dividends and interest calcs which the CGT calculators seem to avoid. AI is suggesting I look at Sharesight as option. I might try it later.

masonic

AI might be useful in cleaning the source exports, but it would require careful checking to ensure it is a faithful reproduction of the original data fed in. It still makes a lot of factual errors and can invent data in the course of performing tasks. If I were going down that route, I would probably look to have Claude Code generate a converter that could combine the exports into a clean csv containing sufficient and consistent information for the CGT calculation.

It is really the understanding of the rules and how they should be applied in a variety of different situations that is the challenge. Dealing with edge cases and changes will require human intervention.

Sharesight might be worth exploring. For £168 per year, their standard plan appears to do some tax reporting. It looks promising in terms of importing data from brokers, so could solve the data cleaning part. From what it shares on its website, I am not so sure it will be able to apply bed and breakfast rules or deal with things like share splits etc to generate a CGT report of the standard that could be used to complete a tax return. But it may help get the data into a good enough state that it could be loaded into a more specialist CGT tool for the calculation itself.