Preparation resource. Editorial review: November 3, 2026. This guide helps organize records and questions; it does not determine your tax position. Use the agency instructions for the relevant year and obtain advice for your circumstances.
Records to organize
Prepare the records that relate to your situation and keep the original supporting statements. Use the same filing year or clearly labelled periods so the reviewer can follow the history.
- 1099-B and complete transaction history
- Purchase confirmations and transferred-account basis history
- Corporate-action, wash-sale and adjustment statements
How to use these records
For each sale, connect proceeds to the purchase lot and any later adjustment. Transferred shares, reinvested distributions and corporate actions can leave gaps in a broker's basis display. Ask the preparer to resolve those gaps before treating proceeds as gain.
The question to resolve before filing
Which transactions have missing or adjusted basis, and what evidence supports each adjustment?
Start with the facts you can support. Identify missing statements, corrections and earlier filings instead of filling a gap with an estimate that has not been discussed. Tell the team which countries, tax years and agencies are involved so the engagement can cover the right work.
A mistake to avoid
Do not assume a blank basis field means the investment cost was zero.
A clear handoff to your preparer
- Label the evidence. Keep each record with its relevant year, account or activity.
- List open questions. Share missing information and anything that differs from the prior return.
- Confirm the scope. Ask which returns, disclosures and follow-up work are included before preparation begins.
Do not enter identity numbers, account numbers, verification codes or tax-document copies in a public enquiry. Use your private client portal for requested records after onboarding.
Official starting points
Use the current agency guidance and the instructions for the applicable filing year. A source link is not confirmation that a particular rule, election or claim applies to your circumstances.