You sell 50 shares of a bank you have been holding for two years. The price on the floorsheet says you sold at a healthy profit over what you remember paying. Then the capital gains tax that Meroshare withholds comes out larger than you expected, and on a later sale of the same stock, smaller than you expected. Nothing about the market changed. What changed was your weighted average cost, and almost nobody explains how that single number decides your tax bill.
The weighted average cost of shares in Nepal, the blended price the system treats as what you paid, is the most important number in your demat account that you probably cannot state from memory. It is not the price on any one of your buy transactions. It is not the price you feel you paid. It is a running average that the Central Depository System and Clearing Limited (CDSC) rebuilds every time you buy, receive a bonus, or take up rights. Your taxable gain is measured against it, and your tax is deducted at the moment of sale based on it.
This piece explains exactly how that average is built, why partial sales behave in a way that surprises people, how bonus and rights shares quietly move it, and where the rules are genuinely unsettled. If you trade NEPSE shares and file nothing further because the tax is withheld for you, this is the mechanic doing the withholding.
What “cost basis” means, and why Nepal uses one blended number
Cost basis is simply the amount the tax system accepts as what a share cost you. Your capital gain is the sale price minus that basis, and the capital gains tax (CGT) applies to the gain, not to the whole sale amount.
The question every tax system has to answer is: when you own many shares of the same company bought at different times and prices, which cost do you use when you sell only some of them? There are a few honest ways to answer. First in, first out (FIFO) assumes you sold your oldest shares first. Specific identification lets you nominate exactly which lot you sold. Nepal does neither for listed shares. It uses the weighted average cost method, where every share of a given company is treated as identical and carries the same blended cost.
This is the point most investors miss. In the tax system’s eyes you do not own a February lot and a July lot. You own one pile of shares at one average price. The moment a new buy settles, the whole pile is repriced.
CDSC and the Meroshare system apply this method when they compute your CGT at sale, per the mechanics documented by ShareSansar and reflected in every NEPSE cost calculator in circulation. The formula is plain: weighted average cost equals total capital invested divided by total number of shares held. Total capital invested is the sum, across all your buys, of quantity multiplied by price, and it includes the broker commission and fees you paid on the way in. Your entry costs are part of your basis, which slightly lowers your taxable gain. That is one of the few small mercies in the calculation.
A worked example, because the formula hides the surprise
Take a real sequence. Suppose you buy shares of one hydropower company three times.
In Mangsir you buy 100 shares at NPR 400 each. In Falgun you buy another 100 at NPR 500. In Jestha you add 200 at NPR 350. Ignore commission for a moment to keep the arithmetic clean.
Your total capital invested is (100 times 400) plus (100 times 500) plus (200 times 350), which is 40,000 plus 50,000 plus 70,000, or NPR 1,60,000. Your total shares are 400. Your weighted average cost is 1,60,000 divided by 400, which is NPR 400 per share.
Now you sell 100 shares at NPR 600. The tax system does not ask which 100. It measures your gain against the blended NPR 400, so your gain is (600 minus 400) times 100, or NPR 20,000. CGT applies to that NPR 20,000. Here is the part that catches people. You might mentally tag those shares as the cheap Jestha lot you bought at 350, expecting a gain of NPR 250 a share. Or you might tag them as the Falgun lot at 500, expecting only NPR 100. The system ignores both. It uses NPR 400 every time.
Add commission back in and the average shifts slightly upward, because the fees you paid on entry are folded into total capital invested. On small trades the effect is minor. On large positions built over many transactions, the commission drag is real and it is working quietly in your favor at sale, since a higher basis means a smaller taxable gain.
The partial-sale trap: your average does not move when you sell
Selling shares does not change your weighted average cost. It only reduces how many shares you hold at that same average. This is the single most misunderstood behavior in the whole system, and the meta-question behind most “why is my CGT wrong” complaints.
Continue the example. After selling 100 of your 400 shares, you have 300 left. Their weighted average cost is still NPR 400. The system did not recompute anything on the sell side except your remaining quantity. So if the price runs to NPR 700 and you sell another 100, your gain is measured against NPR 400 again, giving (700 minus 400) times 100, or NPR 30,000.
People expect the opposite. They expect that selling their “expensive” shares should leave a cheaper average behind, or that booking a partial profit somehow resets the clock. It does not. A sale is a reduction in quantity at a fixed average, full stop. The only things that move your weighted average cost are events that add shares: a new buy, a rights issue you subscribe to, or a bonus.
This also means you cannot cherry-pick a high-cost lot to sell in order to shrink a taxable gain. There are no lots. There is one number, and you already own it.
How bonus shares quietly raise your future tax
Bonus shares feel like a gift, and in cash terms they are. The company issues them from its reserves and you pay nothing. But because your weighted average cost is total capital invested divided by total shares, adding shares that cost you nothing pulls the average down. A lower average is not free. It means a larger taxable gain, and a larger CGT bill, whenever you eventually sell.
Return once more to the 400 shares at an average of NPR 400, total invested NPR 1,60,000. Say the company declares a 20 percent bonus and you receive 80 free shares. Your total shares become 480. Your total capital invested is unchanged at NPR 1,60,000, because the bonus cost you nothing. Your new weighted average cost is 1,60,000 divided by 480, or NPR 333.33.
Every rupee you later sell above NPR 333.33 is now taxable gain, where before the threshold was NPR 400. The bonus increased your share count and lowered your basis, so more of your eventual sale is exposed to CGT. This is not a reason to dislike bonus shares. It is a reason to understand that a bonus converts retained earnings into a bigger future tax event, and to update the figure in Meroshare so the system does not mis-bill you at sale. Multiple Nepali brokers and calculator tools stress that receiving bonus or rights shares alters your weighted average cost and must be reflected in your records.
There is a genuine open question here worth naming honestly. Whether the free bonus shares carry a cost basis of zero or a basis at par value has been treated inconsistently across calculators and commentary, and it changes the arithmetic above. Some tools add bonus shares at zero cost, as done here. Others assign par value to them. The prudent move is to confirm the treatment CDSC actually applies to your holding before you sell a large bonus-heavy position, rather than trusting a third-party calculator. Reformers have separately proposed exempting bonus shares from tax until they are sold, but as of the fiscal year 2083/84 budget that is a proposal, not law.
Rights shares move the average too, but in the other direction
Rights shares are not free. You subscribe to them at par value, and that subscription price enters your total capital invested and therefore changes your average. Whether it lifts or lowers your weighted average cost depends on whether the rights price sits above or below your existing average.
If your average is NPR 400 and you take up rights at par (NPR 100), you are adding shares far below your average, so the average falls, raising your future taxable gain much as a bonus does. The cash you paid for the rights is real and does become part of your basis, but because par is usually well below the market-driven average of a seasoned holding, the net effect is a lower average and a larger eventual gain. If you understand the trade-off between subscribing, selling the entitlement, or skipping it, this tax consequence belongs in that decision, not as an afterthought.
The Magh 2072 line and other edge cases
Two wrinkles matter for anyone with older holdings or messy records.
First, the dematerialization cut-off. CDSC’s clean weighted-average tracking works for shares transacted through the demat system, which for most retail investors means from Magh 2072 (early 2016) onward. Shares acquired or held before that transition do not always carry a reliable system-computed cost, and their basis has historically needed manual declaration and documentation. If you are sitting on very old certificates that were later dematerialized, do not assume the number Meroshare shows is complete. Check it against your own purchase records.
Second, self-declaration. The system computes CGT from the cost information it holds, and where that information is incomplete, investors have at times had to declare their own weighted average cost. A wrong or blank figure does not save you tax. It usually means the system defaults to an assumption that produces a higher taxable gain, so you overpay. Keeping your own running record of every buy, bonus, and rights event is not busywork. It is the only way to check the machine.
For the broader picture of how these gains are then taxed, and at what rate, see our guide to Nepal’s new capital gains tax for 2026/27 and the underlying explainer on capital gains tax on NEPSE.
Why the average interacts with the rate, and why that matters now
Cost basis decides how much of your sale is gain. The holding period decides the rate applied to that gain. The two combine into your actual tax, and both changed meaningfully in the latest budget.
For the fiscal year 2083/84 (2026/27), capital gains tax on listed shares for an individual investor is 10 percent on shares held one year or less and 7.5 percent on shares held more than one year, according to the Himalayan Times and the federal budget highlights published by the Institute of Chartered Accountants of Nepal (ICAN). The same reform made this CGT a final tax for individuals, meaning the amount withheld at sale settles the matter and the gain does not re-enter your annual income tax return.
The holding-period question runs into the weighted-average method in a way people rarely notice. Because your shares are pooled at one average, but their purchase dates are not pooled, the system still has to decide which shares are short-term and which are long-term when you sell part of a blended holding. In practice CDSC tracks acquisition dates lot by lot for the holding-period test even while pricing everything at one average for the gain. That means a partial sale can be split, with some shares taxed at the short-term 10 percent and some at the long-term 7.5 percent, depending on when each tranche was acquired. If you built a position across several months, do not assume a single rate applies to the whole sale. For the mechanics of the two rates, see our explainer on short-term versus long-term capital gains on NEPSE.
The verdict: your basis is the one figure worth tracking yourself
Here is the position, plainly. The weighted average cost of your shares is not a background detail the system handles for you. It is the number that decides how much of every sale is taxed, and it moves in ways that are easy to get wrong: buying more shifts it, a bonus lowers it, rights change it, and a sale does not move it at all. Trusting Meroshare to always have it right, especially on older holdings, bonus-heavy positions, or shares that predate Magh 2072, is how investors end up overpaying or getting surprised at settlement.
The discipline is unglamorous and worth it. Keep your own log of every transaction in a stock: date, quantity, price, commission, and every bonus or rights event. Recompute your weighted average cost after each event. Before you sell a large position, reconcile your number against what the system shows. If they disagree, find out why before the tax is withheld, not after, because a final tax is exactly that, final.
Most retail investors will never do this. That is precisely why the ones who do understand their own basis make cleaner decisions about when to sell, know their real gain before they act, and are never blindsided by a CGT figure they cannot explain.
This is analysis, not financial advice.
