The fee covers custody and administration of the underlying shares. It is typically a few cents per receipt per year and is netted out of the dividend where one exists, or charged to the brokerage account where it does not. Non-dividend-paying ADRs still incur it, which surprises holders who expected a fee-free position.
On low-priced receipts the fee is a meaningful drag. Convert it to a percentage of the position before treating an ADR as equivalent to owning the local line.
Example: a $0.03 annual fee on an ADR trading at $6.00 is 0.5% a year, more than many fund expense-ratio figures, and it is charged whether the receipt rises or falls.
Related: adr, adr-ratio, dividend, expense-ratio, gdr