Can sell more coins than what you have... without warning or raising an exception

[c0indev3l]

Hi,

I think the following code should raises an error or at least display a warning...

import coin2086

columns = ['datetime', 'trade_side', 'cryptocurrency', 'quantity', 'price', 'base_currency']  # price = prix unitaire
data = []
data.append(['2013-01-01 00:00:00', 'BUY', 'BTC', 10, 10.0, 'EUR'])
data.append(['2023-01-01 00:00:00', 'SELL', 'BTC', 11, 15_000.0, 'EUR'])
trades = pd.DataFrame(data, columns=columns)
trades["amount"] = trades["quantity"] * trades["price"]
trades["fee"] = trades["amount"] * 0.0005
display(trades)

year = 2023
allowance = 305  # EUR
form2086, taxable_profit = coin2086.compute_taxable_pnls(trades, year=year)
print(f"Total taxable profit for year {year}: {taxable_profit:.2f} euros")
if taxable_profit > allowance:
    expected_tax = (taxable_profit - allowance) * 0.3
    print(f"Expected tax amount: {expected_tax:.2f} euros")
    print(f"Fill form 2086 with the information below" )
else:
    print(f"Your profit is below {allowance} euros, your do not have to report")
  
display(form2086)

Kind regards

[c0indev3l]

Maybe adding something like

def diff(trades):
  return trades[trades["trade_side"] == "BUY"].groupby("cryptocurrency")["quantity"].sum().reindex(trades["cryptocurrency"].unique()).fillna(0) - trades[trades["trade_side"] == "SELL"].groupby("cryptocurrency")["quantity"].sum().reindex(trades["cryptocurrency"].unique()).fillna(0)

def verify(trades):
  trades_diff = diff(trades)
  neg = trades_diff[trades_diff < 0]
  assert (trades_diff >= 0).all(), f"You can't sell more coins than what you have. See\n{neg}"

should be considered

[fandre90]

Thank you for detecting this bug and opening an issue. It looks like you are right, this is a missing check. Selling more coins than you own can happen on exchanges that support short sells, but coin2086 explicitly does not support this use case, and I have no idea of the tax treatment of such events.

I will have a look at it and add a check to prevent negative balances at any point in time, not just on average.

[c0indev3l]

Hi @fandre90 ,

You are right ! this check shouldn't be made "on average" but at "any point in time"...
Here is an implementation idea for such a check

display(trades)
portfolio = trades[["cryptocurrency", "quantity", "trade_side"]].copy()
display(portfolio)
portfolio["sign"] = portfolio["trade_side"].map({"BUY": 1, "SELL": -1})
portfolio["signed_quantity"] = portfolio["quantity"] * portfolio["sign"]
pivoted_trades = pd.pivot_table(portfolio.reset_index(), values="signed_quantity", columns="cryptocurrency", index="index").fillna(0)
display(pivoted_trades)
display(pivoted_trades.cumsum())
display(pivoted_trades.cumsum() >= 0)
display((pivoted_trades.cumsum() >= 0).all())
display((pivoted_trades.cumsum() >= 0).all().all())
assert (pivoted_trades.cumsum() >= 0).all().all(), f"You can't sell more coins than what you have. See\n{pivoted_trades.cumsum()}"