Tax treatment of trading depends on your country, and this forum cannot give tax advice. What every trader can do is make sure the records are complete and usable.
If you have traded with several brokers or prop firms during the year, a single summary sheet listing each account, its statement files and its currency saves a lot of time when the records are needed.
What brokers typically provide:
Monthly or annual account statements.
Trade history exports (CSV, HTML or PDF).
Sometimes country-specific tax reports.
Things worth checking:
Whether swaps, commissions and deposit/withdrawal fees are included.
Currency of the report and how conversions are handled.
Whether closed accounts can still be accessed later.
Good practice:
Download statements every month and store them outside the broker's portal.
Keep prop firm payout confirmations with the same care.
Note exchange rates used for conversions.
How do you organise your trading records at year-end?
I keep a single sheet with every account, statement file name, currency and the date I last downloaded it. Prop payout emails sit in the same folder as the broker annual PDF so I am not hunting inboxes in April.
Monthly downloads beat year end panic. One broker closed an old login after nine months of inactivity and I would have lost the HTML history without the local copies.
I check that swaps and commissions appear as separate lines, not buried inside a net profit column. Incomplete exports are a problem I can prevent even when I cannot give tax advice.
Closed prop challenges get archived the day the dashboard locks. Waiting until statement season has already bitten me once.
How often do you pull fresh exports? I keep prop and broker files in one tree sorted by firm name.
