For most property, arriving as a resident gives you a tax cost equal to the property's value on the day you arrive, so growth from earlier years is left outside the new country's reach. That is the rule that matters most to people who have owned shares or a home for years before moving. The catch is evidentiary: the reset is only as good as the valuation you can show for that date, and the date is fixed by when residence began rather than by when you decided to move. Establishing both in the year you arrive is much easier than proving them later.
Adjusted cost base — meaning in cross-border tax
The meaning of Adjusted cost base in cross-border tax, and what turns on it.
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The tax cost of property, from which a gain or loss is computed. It resets on arrival in a country and is deemed on emigration.
Why it matters
The recurring theme here is that the source country collects first and the residence country decides how much of that is usable. Category and country limits do the damage.

What one system calls it and the other does not
The dangerous version of this is not a disagreement but a gap: a category that exists in one system and simply has no counterpart in the other. Nothing contradicts anything, so nothing looks wrong, and the position is only tested when an authority asks where the income went.
Where it shows up in practice
The quickest way to understand Adjusted cost base is to see it in place. These are the pages where it decides something.
What to do with it
If this term has turned up in a letter, a slip or an adviser's email and you are not sure which side of it you are on, that is a short call to the helpline rather than a research project. The quote comes before the work, in writing.
The value of naming a concept precisely is that it makes the missing document obvious. Most cross-border problems are not disputes about meaning; they are positions that were correct and could not be shown to be.
Reviewed for the 2025 and 2026 filing seasons by Udit Gupta, International Tax, Cross-Border Tax & Transfer Pricing Expert, Legal Quotient Consultants. This is general information rather than advice about your file — a short call is the way to get the second.
International tax accountant — what this page covers
This is the page to read on international tax accountant. It takes adjusted cost base in order — the test that decides who is affected, the returns and forms that follow from it, and a fee quoted in writing before anything starts.
What these engagements turn on
Fixing an arrival cost for a long-held foreign portfolio
A family arrived holding shares bought over many years through a broker in their former country, with no valuation as at the date residence began. Their first return here used the original purchase costs, which understated their tax cost and exposed growth belonging to the years before the move. We established the residence date from the facts, obtained price evidence for each holding as at that date, rebuilt the cost schedule and amended the return. The engagement produced a schedule by holding that the family now carries forward.
A departure valuation that the destination country ignored
A client ceased residence holding a rental property and a share portfolio, reported the deemed disposition, and sold the property some years later from his new country. That country measured the gain from his original purchase price, not the departure value. We documented both cost figures, the year in which each country recognised its gain, and the relief claimable for tax charged on the overlapping part, then filed on that basis in both places. The outcome was a single documented position for one asset with two cost histories.
Currency movement hidden inside a share gain
A client sold foreign-listed shares at close to the price he had paid and expected no gain. His records were kept in the foreign currency only. Converting each purchase lot at its own acquisition-date rate, and the sale at the rate on the disposition date, produced gains on some lots and losses on others, and a net result quite different from the one his statement showed. We rebuilt the lots, documented the rates used and their source, and filed the computation with the return.
Rebuilding the running cost base of reinvested fund units
A holder of mutual fund units had reinvested distributions for years and reported a sale using the price originally paid, which overstated the gain substantially. We worked through each year's slips, separating reinvested amounts that increase cost from returns of capital that reduce it, and produced a running schedule to the date of sale. The corrected computation supported an adjustment request. The engagement produced the schedule, the slip-by-slip working behind it, and a note on maintaining it for the remaining holdings.
Improvements expensed for years and then needed as cost
An overseas rental property was being sold. Its owner had treated every roof, window and kitchen as a repair on annual returns, and now wanted the same spending counted in the cost of the property. Both at once was not available. We sorted the spending into what had genuinely been maintenance and what was capital in nature, checked what had already been claimed against rental income, and computed the cost on a basis consistent with the returns already filed. The engagement produced that reconciliation and the supporting invoice file.
Different cost bases for the same inherited holding
A client inherited shares from a parent who had been resident elsewhere. One system treated the shares as acquired at their value on the date of death; the other carried the deceased's own cost forward to the heir. She therefore held one asset with two different tax costs and a sale in prospect. We set out each figure, the year each country would recognise a gain, and what relief for the other country's tax would and would not cover, so the timing of the sale became a decision rather than an accident.
One Salary, Two Countries Claiming It
A US citizen resident in Canada, taxed in full on both sides because each return was prepared without the other in view. Deciding which country has the first right to the income, then claiming relief on the second return in the right order, is what stops the same dollar being taxed twice.
Read how this one runsSocial Security Contributions Owed in Two Countries at Once
A totalization agreement assigns contributions to one system and exempts the other, but only against a certificate obtained in advance. Without it both sets come out of the same salary and neither is straightforward to recover.
Read how this one runsAll case studies — every published engagement in one place.
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Related-party purchasing, customs value versus transfer price, and foreign-affiliate structures put trading businesses inside the s.247 documentation rules.
Goods crossing a border move the tax question from income to indirect: registration thresholds, place of supply, the customs value and the transfer price between related entities all have to agree with each other. When they do not, the adjustment arrives from two authorities at once and each one uses the other's number.
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What people ask us about Adjusted cost base
The cost is fixed in your reporting currency on the day the property was acquired, and the proceeds are fixed on the day it was sold. Because those are two different rates, currency movement between them forms part of the gain or loss, even where the price in the foreign currency never moved. Converting both ends at one rate — usually the rate at sale, because that is the one you know — quietly removes that element and produces a figure that cannot be reconciled to either country's records. Each acquisition lot needs its own rate.
On emigration most property is treated as sold at its value on the day you cease to be resident, whether or not anything was actually sold, and the gain to that point falls into the departure year. Your cost for anything you keep becomes that same value. The difficulty is that the country you move to may not accept the new figure, and may measure a later sale from your original cost instead. That is one asset with two cost bases, and the overlap is what treaty relief has to be built around, using valuations made at the time.
Almost always because the two countries start counting from different costs. One may have given you a fresh cost on arrival or a deemed cost on departure; the other may still be working from what you originally paid, many years earlier, in its own currency. Neither is wrong on its own terms. What matters is that you know both figures before you sell, because relief for the tax the other country charges is limited by category and by country, and a gain recognised in one year and not the other can strand that relief entirely.
With whatever was contemporaneous: the purchase contract, the bank transfer, the broker's confirmation, the completion statement, and for improvements the invoices rather than a later estimate. Where nothing survives, the honest position is a reasoned reconstruction, documented as such, rather than a round figure entered on a return. For property held through a period of arrival or departure, a valuation prepared at the time is worth more than the same exercise done under examination. The evidence you can produce, not the amount you remember spending, is what fixes the cost.
Yes, and this is a common reason a gain is overstated on a return. Distributions that are reinvested buy more units, and the amount reinvested is added to your cost; distributions that are a return of capital reduce it. Both are reported to you annually and both are easy to ignore for years. By the time the holding is sold the running total sits in a stack of annual slips rather than on a statement, and the figure a broker prints may reflect neither. Rebuilding it is only arithmetic, but it has to be done year by year.
It depends on the country, and a day count is only ever the start. Many use a threshold in a tax year, some also look at averages across several years, and some have no day test at all and decide on where your home and life are. Two countries can both conclude you are resident, which is what the treaty tie-breaker exists to settle. Counting days without checking the tie-breaker is how people end up filing as resident nowhere. See the residency tie-breaker.
The inheritance itself is often not income to you, but three other things can create tax: the estate may owe tax where the deceased or the property was situated, some countries tax the recipient directly, and the gain from the date you inherit to the date you sell is yours. Reporting obligations can also attach to holding the asset. See inheriting property abroad.



