I recently closed some positions on IB that were a few years old due to rebalancing.Overall no problem, but the cost basis was slightly off. both in per share (~172) and in proceeds (~518), as you can see in a montage from two activity statements from 2022 and 2024 (all numbers in USD):
Obviously the absolute amount of the difference is tiny, but this difference makes it impossible for my bookkeeping system (beancount) to find the correct lot to be closed. I have to manually adjust either the open or close price.
Now this happens for about every sell transaction, that the cost basis numbers are ever so slightly different. I inquired with IBKR support, but no reply so far.
Anyone else observes the same thing? should the cost basis not stay constant over time/ reports?