One paper file per property. All paperwork sorted in chronological order.
One excel spreadhseet contains for one record for any and all IP related transactions which contains the following information;
property name
transaction amount
expense type
rent
date
supplier/payer
account name where payment came from
PAYG income
PAYG tax paid
Expense types are those generally required to be submitted in the tax return however there is some additional informaiton eg property management fees, PM postage/admin, water rates, council rates, taxes (eg land tax), depreciation, maintenace, interest, bank fees, insurance, body corporate fees, BC special levies, accountancy costs, 'other'.
So at any time during the year, based on a pivot table I can simply see where my tax return is.
The biggest time is setting it up and then doing it every month to update all tranactions only takes 10-15 minutes max.
The next step is to start putting in anticipated & future amounts for all expenses, almost like having an entire years budget. But that's a bit of work