When You Can't Prove What You Paid

You have decided to sell the shares. Or the investment unit, or the block you have owned since before the kids were born. You ring the broker, or the agent, and then somebody asks the question that stops everything: what did you pay for it?

And you do not know. The contract note was in a folder that went out during the downsize. The bank has changed systems twice. Your husband handled all of that and he died four years ago.

This is not carelessness. It is arithmetic. Thirty years is a long time to keep a piece of paper, and retirement is exactly when the assets bought decades ago finally get sold. The problem sits dormant for a working lifetime and then arrives all at once.

Here is how to deal with it. This is general information, not personal financial advice, and it is not tax advice — cost base work belongs with a registered tax agent, and this article is about what to do before you get there.

First: check whether it is even a CGT asset

Before reconstructing anything, check the date. Capital gains tax does not apply to assets acquired before 20 September 1985 (ATO, https://www.ato.gov.au/individuals-and-families/investments-and-assets/capital-gains-tax/acquiring-cgt-assets, as at August 2026). That is the day the system started, and anything you acquired before it is generally a "pre-CGT" asset.

For a retiree this is the single most valuable thing to establish, because it does not solve the record problem — it removes it. If the asset is pre-CGT, you are not reconstructing a cost base at all.

Two qualifications worth knowing. Major improvements made to a property since that date may still be caught, so a pre-CGT house with a post-CGT extension is not automatically clean. And the acquisition date is the contract date, not the settlement date — which decides the question for anything bought around that September, and matters generally because it also sets the clock for the 12-month holding period.

What a cost base actually includes

If the asset is post-CGT, the next thing worth knowing is that the cost base is more than the purchase price, and people reconstructing from memory almost always understate it — which inflates the gain against themselves.

The cost base includes the money you paid and the market value of any property you gave to acquire it, plus incidental costs you incurred when you acquired the asset or when the CGT event happened (ATO, https://www.ato.gov.au/individuals-and-families/investments-and-assets/capital-gains-tax/calculating-your-cgt/cost-base-of-asset). Brokerage, stamp duty, conveyancing and legal fees, transfer costs. It excludes anything for which you can claim a tax deduction.

So the search is not just for a price. It is for the whole transaction.

The five-year rule almost everyone reads backwards

This one is worth stopping on, because it is the reason a lot of records get thrown out.

You must keep records of every act, transaction, event or circumstance relevant to working out a capital gain or loss, in English or readily translatable. And the ATO is explicit that you need to keep records for five years after the year in which the CGT event occurs, with penalties applying if you do not keep them for at least five years after the relevant CGT event (https://www.ato.gov.au/businesses-and-organisations/preparing-lodging-and-paying/record-keeping-for-business/detailed-business-record-keeping-requirements/running-your-business-records/income-tax-return-records-business/stock-and-asset-records/capital-gains-tax-asset-records, as at August 2026).

Read that carefully. Five years runs from the CGT event — the sale — not from the purchase.

Which means that for an asset you bought in 1994 and sell in 2026, the 1994 contract note needs to survive until the early 2030s. Not five years. The whole holding period, plus five.

A great many people believe the opposite: that after five years the purchase paperwork can go. If you are about to clear out a filing cabinet — and if you are downsizing, you are — this is the rule to have in mind before the recycling bin arrives. Our article on clearing the family home covers the rest of that process, but this is the one box not to tip.

One extension worth knowing if you have ever crystallised a loss: where you have applied a net capital loss, the ATO's guidance is that you should generally keep the records of the CGT event that produced that loss until the end of the period of review for the income year in which the loss is fully applied — which can run well past the usual five years.

The way to stop keeping paper forever

Here is the part that turns the rule above from a burden into a task with an end, and it is not widely known.

The ATO allows a CGT asset register. If you enter all the necessary information about an asset in the register, the entry is in English and is certified in writing by an approved person — a registered tax agent, for example — and the entry is certified after 31 December 1997, then you can discard the underlying CGT records five years after that certification (ATO, CGT asset records).

That is the permanent fix. Instead of guarding a 1994 contract note until the 2030s, you have the information transcribed into a register, get it certified once, and the original paperwork stops being the thing your tax position depends on. For anyone holding assets bought decades ago, this is worth raising with your tax agent — it is the difference between a filing problem that lasts the rest of your life and one that is finished.

The ATO may already have some of it

Here is the practical tip most retirees do not know about, and it is free.

The ATO holds third-party reported data for share, stapled security and unit transactions, and you can look at it yourself. Log into myGov, go to the Australian Taxation Office under linked services, and select Shares and unit records. Choose a period from the drop-down or enter the dates, select Search, tick the securities you want and download them (https://www.ato.gov.au/online-services/online-services-for-individuals-and-sole-traders/ato-online-services-and-mygov/using-ato-online-services/your-securities-records-in-ato-online, as at August 2026).

One caveat, and it is the ATO's own, so take it seriously: "you should not rely only on the information in these records and must review your own records to verify that the information is complete and correct."

So treat this as a starting point rather than an answer. It will not reach back to a purchase made in the 1980s, because it reflects what has been reported to the ATO. But it takes ten minutes, it is free, and for anything bought more recently it may hand you a substantial part of what you are missing.

Where else to look

The ATO's own suggestion is a good place to start: ask your solicitor, estate agent, builder, stockbroker or investment adviser for copies of the records they hold. Professionals often keep files far longer than their clients assume.

Beyond that, and in rough order of how often they work, the share registry is usually the best single source for long-held listed shares, because registries hold holding history including issues, splits and reinvestments — ask early, because it can take weeks. Old tax returns and notices of assessment may not give you a price, but they often establish the year you acquired something and sometimes the income it produced from the first year of ownership. Bank and passbook statements showing the money going out are valuable, because a dated payment plus a known contract date is often enough to work with. The conveyancing file for a property is worth chasing, since solicitors frequently retain these long after you would expect. Historical price data helps where you know the date but not the price. And company and registry announcements covering splits, consolidations, bonus issues, demergers and capital returns matter more than people expect — every one of them changes the cost base, and every one is easy to forget happened.

If the asset was inherited, the rules are different again and depend on when the deceased acquired it — our articles on the cost base of inherited assets and on inherited asset CGT rules for beneficiaries cover that, and it is worth reading before assuming your own purchase date applies.

The dividend reinvestment problem

This is the big one, and it catches people who think their records are fine.

If you have been in a dividend reinvestment plan, you do not own one parcel of shares. Every reinvested dividend is a separate acquisition — at that day's price, on that day's date. Thirty years of reinvestment produces dozens of separate parcels, each with its own cost base, its own acquisition date, and its own eligibility for the CGT discount.

People say "I bought 10,000 shares in 1996." What they actually own is 1996's parcel plus sixty more, accumulated a few hundred dollars at a time. Reconstructing that from scratch is a genuinely large job, and the registry is usually the only realistic source.

Our article on dividend reinvestment plans covers whether to be in one; once you have your parcels identified, our article on which parcel to sell covers what to do with them.

Worked examples

Two people facing the same missing paperwork, with opposite amounts of work ahead. Illustrative only, and not tax advice; no dollar amounts are used because nothing here turns on the size of the gain — it turns on dates and evidence.

Consider Margaret, 74, widowed, who wants to sell a long-held parcel of bank shares her husband bought in the mid-1990s and which has been on a dividend reinvestment plan ever since. She has no contract note. What she actually holds is not one parcel but dozens, each with its own acquisition date and cost base. Her realistic sequence is the registry first, because it holds the holding history and can take weeks to produce it; then the ATO's own securities records via myGov for anything recent enough to have been reported, remembering the ATO's warning that she must not rely on those alone; then her old notices of assessment to pin down the year. On these facts, starting months before she wants to sell is generally rational — after the sale the tax is crystallised and the lodgement clock is running, and the registry still takes just as long.

Now consider Robert, 79, who is selling a block of land his parents transferred to him and assumes he faces the same exercise. The first question is not what he paid but when the contract was signed — because an asset acquired before 20 September 1985 is generally outside CGT altogether (ATO). If the contract predates that day, there is no cost base to reconstruct and the problem disappears. Two things still need checking: whether major improvements were made after that date, which can be caught, and that it is the contract date rather than settlement that governs. On these facts, establishing the acquisition date before doing anything else is generally rational, because it is the one finding that can make the entire reconstruction unnecessary.

Do this before you sell, not after

This is the practical heart of it.

Reconstruction takes time you will not have once the sale has happened. Registries take weeks. Solicitors take longer. If you start after the CGT event, the tax is already crystallised, the lodgement deadline is running, and you have lost the ability to do anything about it.

Start before, and the whole thing changes. You can time the sale. You can choose which parcels to sell deliberately rather than by default. You can find out that half of it is pre-CGT and stop worrying. And if it turns out the reconstruction is genuinely difficult, you find that out while you still have options.

The general position is that you need to be able to support the figures you put in your return with reasonable evidence. A number you cannot evidence is not a reconstruction — so give yourself the months it may take.

Afterwards: put it somewhere it will survive

Once you have reconstructed a cost base, that reconstruction is now a valuable document — for you, and later for your executor, who will otherwise have to do the whole exercise again with even less to go on. This is also the natural moment to ask your tax agent about certifying it into a CGT asset register, so the reconstruction becomes the record rather than a set of notes about records.

Keep it with your other essential records rather than in an email folder. Our article on the emergency information folder covers where that should live, and our article on digital legacy planning covers making sure someone can actually get to it.

And one note for after the sale: the proceeds land in your bank account, where they are an assessable asset for the Age Pension — the means-tested payment administered by Services Australia — and subject to deeming. If you are on a part pension, that is worth modelling before you sell rather than discovering at the next review; our article on deeming rates sets out how that works.

The one-line version

Check the acquisition date first, because a pre-CGT asset removes the problem entirely; keep purchase records for the whole time you own the asset plus five years after you sell it, or get a certified asset register so you don't have to; and start reconstructing months before the sale, beginning with the ATO's own records and your share registry.

Sources

• ATO — Acquiring CGT assets
• ATO — Cost base of assets
• ATO — Records of capital gains or losses from capital gains tax assets
• ATO — Keeping records of shares and units
• ATO — Your securities (share and unit) records in ATO online
• ATO — Cost base of inherited assets