Start with the evidence
Find the current source document and identify the service period. Compare the charge with the agreement, including any documented change, rather than assuming last month’s amount remains correct.
Work through the example
A service was USD40 last month and USD45 this month. The USD5 difference calls for a source explanation, such as a documented plan change; repetition alone does not validate it.
Make the next step clear
Keep the explanation and relevant service document together. If the charge is unexpected, assign a question to the service owner rather than silently treating it as an approved increase.
Keep the source context
These guides concern the evidence behind a business record. A receipt, a reimbursement request and a bank movement may describe related parts of one event, but they are not interchangeable documents. Keep each source and its role visible.