Why is this bill higher than last time?

Compare matching parts

A higher bill can come from a longer period, greater usage, a changed rate, an added item or a changing credit. Put earlier and later bills side by side. Copy the service dates, currency and totals. Count the days covered when periods differ. Keep previous balances separate from new charges so the comparison describes matching parts of the bills.

Worked example with made-up figures

Repeating

Fictional sample rent: A$270.97 / week
Telco One: A$11.06 / week
Fictional sample groceries: A$9.65 / week
Streamly: A$3.16 / week

Together A$294.84 a week.

Get your own answer, first one free

Split the total into rows

Make a paper table with one row per charge type. Copy fixed charges, usage charges, one-off items, labelled tax amounts, discounts and credits separately. Treat a credit as an amount subtracted from the total. Write earlier amount, later amount and difference in three columns. Add those differences to see whether they explain the total change. Keep original labels beside your figures.

Separate quantity and rate

For usage lines, copy quantity, unit and price per unit from each bill. Multiplying quantity by rate gives a basic charge when the line uses that calculation. A longer period may produce more units even at the same daily use. Fixed charges may also depend on days covered. Keep minimum charges and adjustments in their own rows, following the bill labels.

Example: made-up figures

Suppose the earlier bill covers 100 units at 2 currency units each, plus a fixed charge of 20. Its total is 220. The later bill covers 120 units at the same rate and fixed charge, giving 260. The increase is 40: twenty extra units multiplied by 2. In a separate rate-change example, 100 units at 3 plus the fixed 20 would total 320, a rise of 100 explained by the changed rate.

Reconcile the amount due

If an earlier bill included a credit of 30 and the later bill shows zero credit, that change increases the amount payable by 30. An unpaid previous balance can also raise the total due while new charges stay the same. Record these separately. Add all differences, including rounding, and compare the sum with the total increase. Retain any unexplained remainder as a number beside the relevant lines for checking.

Keep a record of your check

Write the document dates and page numbers beside your notes. Trace each copied amount back to its original row, then repeat the addition and subtraction once. Keep estimates visibly labelled and retain the original units. This leaves a clear record of which numbers came from documents and which came from your calculation, so another person can follow the same steps with the same papers.