The question your broker does not answer
A broker shows the realized gain on a sale: what you received minus what you paid. That number answers whether the trade made money. It does not answer whether selling was better than keeping the shares.
To answer that, follow the shares after the sale. Portle compares three values for every sale, all measured today: the shares if you had kept them, the cash you received, and that cash if you had put it in the market.
Value the shares you sold as if you still held them
Start with the quantity you sold. Apply every split after the sale date, add every dividend those shares would have paid, and multiply the final quantity by today’s price. Leaving out dividends makes selling a dividend stock look better than it was, every time.
The sale date matters for the first day. If you sold on a trading day, that day’s split or dividend is not counted, because a seller on the ex-dividend date is not the holder of record. If your ledger shows a settlement date that fell on a holiday, the next trading day’s split and dividend are counted.
Compare with the cash, then with the market
The cash baseline is the money you received after fees and tax, with no interest added. It makes the smallest assumption, because you actually received it. Cash minus the value of the kept shares is the headline result: positive means selling left you better off, negative means keeping the shares would have been better.
The market baseline assumes you put the same cash into your benchmark on the sale date. Market minus the kept shares shows the result for someone who reinvests. Portle shows both side by side and does not pick one for you.
Worked example: three sales
You sold 20 shares for $2,995 after fees. Since then the stock paid $1.00 per share in dividends and trades at $190. Kept, the shares are worth $3,800 plus $20 of dividends, $3,820. Against cash, the sale cost you $825. If the benchmark rose 18%, the cash would be $3,534.10 in the market, still $285.90 short. Both baselines agree that keeping the shares would have been better.
You sold 10 shares for $3,990. A 4-for-1 split followed and the stock now trades at $80, so the kept shares are 40 × $80 = $3,200. Against cash, the sale is $790 ahead. A third sale received $1,000; the stock rose 10% afterwards and the benchmark 25%. Kept, it is $1,100, so cash is $100 behind but the market is $150 ahead. When the two baselines disagree, the verdict depends on where the money went.
Sales that cannot be measured are left out, not counted as zero
A sale is excluded when the stock has no price history, when its history starts after the sale date, when today’s price is missing, or when an exchange rate is unavailable. A history that starts late would miss splits and put the kept value off by a whole multiple, so it is safer to leave the sale out and say so.
When the benchmark price is missing, only the market baseline is left blank. The cash baseline does not depend on the benchmark and still appears. Portle states how many sales were excluded and how many had baselines that disagreed.
What this review does not tell you
The kept value uses today’s exchange rate, while the cash and market values use the rate on the sale date. When the stock trades in a currency other than your reporting currency, exchange-rate moves after the sale land only on the kept side. For a US investor selling US shares, or a Korean investor selling Korean shares, this does not arise.
In Portle, the sell timing review is a free card next to realized gains. It needs only your ledger and the price history Portle already has, so no extra data is requested. The best and worst sales are named only when both baselines agree.