Start with a complete period
A statement is a record of movement, not a ready-made budget. Download one complete month for each account used for everyday spending. If a month included a move or a large celebration, keep it in the record but mark the unusual items. Deleting them makes the history neater and the next estimate less useful.
Put each purchase into a small number of meaningful groups: housing, food, transport, other commitments and flexible purchases. Too many groups make the first pass slow. You can split a category later if the distinction changes a decision.
Remove double counting
A transfer between your own accounts is not new income or household spending. Likewise, if the purchases on a credit card are already included, the payment from your current account to that card should not be counted as another set of purchases. Keep the payment visible in a cash-flow calendar because the date still matters.
Suppose account outflows total $2,650, including a $300 transfer to another account and a $450 card payment. If the underlying $450 of card purchases are recorded separately, the combined spending total is $2,350: $2,650 minus $300 minus $450 plus $450. Savings transfers need a place in the plan, but a different label from consumption.
Turn history into a forecast
Use the cleaned totals as evidence, then adjust for the month ahead. A train ticket bought for a one-off visit does not necessarily repeat. An annual membership absent from this statement may still need a monthly reserve.
Keep a short note beside each adjustment. After the next month, compare the forecast with actual purchases and investigate the largest differences first. A useful statement-based budget gets more accurate through explanation, not by forcing every month to look identical.
