Paying taxes with IBSJ… gross/net?

Hi, hopefully a quick question for those who know how US citizens need to keep track of their capital gains liability.

I’m using Interactive Brokers Japan and putting my purchases and sales into a spreadsheet to keep track of cost basis and capital gains. When recording my investment purchases, do I need to record my gross or net amount of JPY used? Likewise, when recording my sales, do I need to record the gross or net amount of JPY used? There are minor fees associated with each purchase and sale which was not the case when I previously used Vanguard, so I’ve only ever had one number I needed to record.

I’m assuming when purchasing (VT) I record the gross amount spent? And when selling I record the net amount?

Hopefully this question is clear. I’d appreciate any help!