Share the action, not every account detail
A household calendar entry can say “Water, $32 due Friday; Sam checks the payment.” Leave account passwords, full card numbers and personal purchases out of that entry. Ask what the other adult will actually need to do. Seeing that the bill is covered requires less access than changing the account settings.
Give the other person enough evidence
If Jo needs to plan household spending, Sam can share the amount, period and relevant due date. If Jo must challenge a charge, the provider may require its own authorization. Ask about a separate account role or contact permission instead of giving Jo Sam's password and hoping it works.
Prepare for absence without widening access casually
If the other adult needs regular account access, check whether the provider offers a separate authorized login. For a one-time question, the account holder can send the relevant line of the statement. Remove unrelated personal information from any copy you share.
For a one-week trip, a narrow arrangement might be “Jo checks Friday’s payment and calls Sam if it is missing.” For ongoing shared responsibility, find out whether each adult can receive their own statement or alerts. Review who still receives those notices after roles change or someone leaves the household.