Cost basis is what you paid for an asset, adjusted for fees. Tracking it across exchanges means keeping one running record per asset instead of trusting each platform's separate view. No exchange sees your full picture: Kraken only knows what happened on Kraken. If you bought the same coin on three platforms and moved some to a hardware wallet, your true basis lives in your own spreadsheet, not in any app. Get that record right and tax season stops being a scavenger hunt.
Why exchange statements don't add up to a cost basis
Each platform reports its own trades, deposits, and withdrawals. None of them know what you paid elsewhere. That isn't a flaw you can complain your way out of; it's how separate custodians work.
What each exchange actually knows
Kraken knows your buys, sells, and the fees you paid on Kraken. It doesn't know you transferred those coins in from another venue at a different price. When you later sell, the platform reports proceeds, but the basis side of the equation is yours to supply.
The transfer trap
Moving coins between exchanges isn't a taxable event in most jurisdictions, but it breaks the paper trail. Your receiving exchange records an incoming deposit with no purchase price attached. Miss that link and you'll later report a sale with a basis of zero, which inflates your gain.
The three numbers you need for every lot
A lot is a batch of coins bought at one time and price. For each one, capture three things:
- Date and amount acquired — including the exact time if you bought more than once that day
- Total cost in your currency — the trade price plus the fee you paid to buy
- Where it went — which exchange or wallet currently holds it, and any transfers since
A lot without a location is a lot you'll lose track of. Write down the destination every time you move something, even a test transfer.
A concrete scenario: two exchanges, one coin, one mess
Say you buy 0.1 BTC on Kraken for $4,000 including fees in March. In July you buy another 0.05 BTC on a second exchange for $2,300. In October you move the 0.05 to Kraken and sell it for $2,600.
Kraken's records alone show a deposit of 0.05 BTC and a sale at $2,600, with basis unknown. Report it wrong — say, using Kraken's first lot price by accident — and your gain looks smaller than it is. The correct basis is $2,300, so the real gain is $300. Small numbers here, but scale that mistake across a year of trades and the error compounds. One reader caught a $2,400 discrepancy this way, purely from a transfer he'd forgotten to annotate.
Choosing a method and sticking to it
Most tax authorities let you pick a cost basis method — FIFO (first in, first out), specific identification, or an average cost approach in some places. The rule that matters: pick one, apply it consistently, and document the choice.
FIFO vs. specific identification
FIFO sells your oldest lots first. It's simple, but it can produce larger gains if you bought early and cheap. Specific identification lets you choose which lot you're selling, which can reduce your taxable gain — but only if your records can prove which lot it was. That means lot-level tracking, not a single average number.
Where the record should live
A spreadsheet works. So does dedicated crypto tax software. What doesn't work is relying on memory or on one exchange's export. Keep your own master file, update it monthly, and back it up somewhere that isn't your laptop.
| Record type | Who holds it | Gap to watch |
|---|---|---|
| Buy price and fee | You (from exchange export) | Fees often excluded by default |
| Transfer history | You | Receiving exchange shows no basis |
| Sale proceeds | Exchange | Basis column blank or zero |
Frequently asked questions
Do I need to track cost basis if I never sell?
Strictly speaking, no taxable event has occurred, so nothing needs reporting yet. But the record still matters, because you'll need it the day you do sell or swap. Reconstructing years of purchases later is painful and error-prone. Build the habit now while the trades are fresh.
Does moving crypto between exchanges reset my cost basis?
In most tax regimes, a transfer between wallets you control isn't a disposal, so the basis carries over unchanged. The coin keeps its original purchase price and date. What changes is only where it's held — and that's exactly the detail people forget to log.
What if I've already lost track of some purchases?
Start with exchange exports and bank records, which usually go back far enough to reconstruct most buys. Where records are genuinely missing, work with a tax professional rather than guessing. Partial records beat none, and honest reconstruction is far better than a fabricated number.
Should I include trading fees in my cost basis?
In many jurisdictions, fees paid to acquire an asset can be added to its basis, which slightly reduces your eventual gain. Rules vary by country, so confirm with a local tax advisor. Either way, record the fee separately so you have the option.
Open your spreadsheet today and add one column: "location." Then backfill it for every lot you currently hold.