Agree how the cost will be handled
Before work starts, decide with the client whether AI usage is included in your fee or charged separately. A clean usage record cannot resolve an unclear commercial agreement. If you use a markup, explain it in that agreement rather than hiding it in a token count.
Record only what the invoice needs
For many engagements, the useful supporting record is a client reference, date range, request count, token totals and API cost. Prompts and model responses are not needed to explain the arithmetic. Keeping the export limited to metadata also avoids casually attaching sensitive working material to an invoice.
Separate the base cost from your markup
Input, cached input and output tokens have different rates. Check that cached tokens are not counted again as uncached input. Show the API cost and your client-billing amount in distinct columns. Redline’s planned export uses consultant-defined markup for this purpose; it does not alter the service’s charge to your account.
Review the boundary conditions
Check the timezone and the start and end of the export period. Confirm that late work has not been omitted and that requests for another client used a different key. Treat the result as an attachment to your own invoice, with tax and accounting treatment handled through your normal process. A few minutes of review makes the record much easier to defend later.