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Robinhood Capital Gains Estimator

Parse Robinhood transaction CSVs to estimate capital gains for the current year

Usage

  1. Download Robinhood "account activity report" transaction CSVs covering the history of your account. You may need to make multiple requests, for example one per year.
  2. Run robinhood_capital_gains_estimator.py transactions.csv to calculate long and short term capital gains for the current year. You can pass in multiple files, or a directory of CSVs. Pass multiple files in chronological order, or if passing in a directory, name the enclosed CSVs such that when sorted by name, they will be in chronological order.

Notes

This script calculates an estimate for capital gains given the provided data, but it may not match the final values calculated by Robinhood. For example, Robinhood does not always provide cost basis data for older transactions in their account activity reports. In such cases, the script simply assumes a cost basis of 0. Some other transaction types such as SXCH and MRGS are also processed with cost basis assumed to be 0. There may also be some transaction types that this script is not aware of. For example, this script has not been tested with stock options transactions. In addition, this script assumes FIFO transaction ordering.

How it Works

Data structures

  • Lot class:
    • prev_lot (Reference to previous Lot)
    • instrument (Instrument name i.e. AAPL or SPY)
    • purchase_date (Date when shares purchased)
    • purchase_price (Price per share when purchased)
    • quantity (Quantity of shares)
    • sell_date (Date when shares sold)
    • sell_price (Price per share when sold)
    • next_lot (Reference to next Lot)
  • lot_roots (dict with references to the oldest Lot for each instrument)
  • lot_heads (dict with references to the newest Lot for each instrument)
  • current_quantities (dict containing the current quantity of each instrument)

Algorithm

  • Iterate through transactions (Buy, CONV, SXCH, MRGS, Sell, and SPL) to build up a chain of lots for each instrument
    • If the transaction is a Buy, CONV, SXCH, or MRGS transaction, a new Lot is created and appended to the end of that instrument's chain. The purchase_price is set to 0 for CONV, SXCH, and MRGS transactions (inaccurate but easier to handle).
    • If a Sell transaction, the Lot chain is traversed from its ROOT, marking lots as sold until the amount in the Sell transaction is fully allotted. If this causes a Lot to be only partially sold, that Lot is split into two lots, with the first Lot completely sold and the second Lot completely unsold.
    • If a SPL transaction, the Lot chain is traversed from its HEAD until a sold lot is found, multiplying quantity of each unsold Lot by the split_ratio. current_quantities is also updated to store the new quantity of that instrument.
  • To calculate capital gains for current year, start at the HEAD of each instrument, iterate backwards until a sold lot is hit, then start counting profits per lot until hitting a lot sold prior to the current year.

Improvements

Reverse splits (SPR) are not yet supported.

Currently, dividends (CDIV) and stock lending income (SLIP) are ignored. These could be tracked and included in the output.

Robinhood seems to have a bug where their stock split (SPL and SPR) transactions are logged to 4 decimal places, even though shares are held to 6 decimal places. This can cause stock split calculation errors. This script currently checks for such situations and prompts the user to input the correct split ratio. I have submitted a bug report to Robinhood, so hopefully this will get resolved in due time.