Give every date a document reference
For each account communication, record the authority, taxpayer or entity, period, action, and stated date. Link the calendar entry to the source letter. A general reminder to deal with taxes is too broad when several accounts require different tasks. Distinguish an official date from a personal target for gathering information, and avoid transferring an instruction from one notice to another.
Make the next responsible action visible
Add the person responsible for a retrieval, review, response, or follow-up only after that responsibility is understood. Mark whether a task is planned, supplied, submitted, or answered. If new correspondence changes the question, preserve the earlier entry and document the update. A shared calendar does not establish that a professional engagement covers every listed account. Ask how new letters would be handled and keep confirmations beside the task they evidence. The official communication remains the source for any required action or deadline.