# Balance Accounting

#### Balance Accounting

A `baseBalances` mapping stores the time-discounted cumulative yield earned at the latest `transfer`, `mint` or `burn` for an address. When multiplied by the cumulative yield, this `baseBalances` mapping returns the accrued rewards. To avoid any rounding errors caused by storing this intermediate state between `balanceOf` reads, `baseBalances` is stored in 27 decimals. This gives high enough accuracy so that the 18 decimal values returned by `balanceOf` are always accurate when formatted to 18 decimals. `WadRayMath` is used to convert and operate on and 27 and 18 decimal values.