Every buy and every sell pays a tax. The rate is set at deployment, between three hundred and eight hundred basis points, and is fixed for the life of the coin. The tax is taken in the pair asset, never in the coin, so the pot is always a balance of the pair asset.
tax = pairAmount × taxBps ÷ 10000
The whole tax goes into the pot and waits for the pour.
toPot = tax