Because it is high volume, repetitive and full of exceptions. Instalments, sibling discounts, bursaries and mid-term joiners each need a different number, and the source of truth is usually one person's spreadsheet.
Arrears are then chased from a second spreadsheet, and the two are reconciled at the end of term when it is least useful.
The fee schedule bills from what was actually offered, including the concession applied, on the instalment dates you set. A mid-term joiner is pro-rated from the record rather than from a calculation somebody performs.
Arrears are live per family, with the ageing visible during the term rather than in a report at the end of it.
It is not a student information system and it does not manage admissions — Flow handles enquiry to enrolment, and the fee schedule follows the accepted offer.
And it does not chase parents for you. It gives you accurate, current arrears, which is the part that usually is not true.
Budgets and cost centres run per department, so spend against budget is current rather than quarterly. Restricted funds are tracked against the ledger they belong to.
Payroll postings from Nest land on the same books, so staff cost by department needs no separate reconciliation.
Products, not integrations. Each one reads the same record, so a join is a permission rather than a sync job with a mapping screen behind it.
Yes, billed from the accepted offer, including sibling and bursary reductions.
Yes, per family, during the term rather than after it.
Yes, through cost centres and budgets against the ledger.
Half an hour on your own numbers is usually enough to say whether Books is the right place to start.