Business use: the logbook, the diary and floor area

The rule

1. Keep a logbook for at least 12 continuous weeks that represents your travel through the year, and you can use it to work out your claim for 5 years.

   ›What the ATO says

   “You must keep the logbook for a period (at least 12 continuous weeks) that is representative of your travel throughout the year. You can then use this representative period to calculate your claim for 5 years if you:”

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2. You may start a new logbook at any time.

   ›What the ATO says

   “Each logbook you keep is valid for five years, but you may start a new logbook at any time.”

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3. A diary for a representative 4-week period can show how you use your home for business, as a pattern of use for the whole year.

   ›What the ATO says

   “One way you may be able to do this is by keeping a diary for a representative 4-week period, showing how you use your home area for business purposes. You can then apply that as a pattern of use for the whole year.”

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4. Without an itemised bill, a diary for a representative 4-week period can work out your pattern of business calls or internet use through the year.

   ›What the ATO says

   “If you don't have an itemised bill or a data breakdown, you can keep a diary for a representative 4-week period to work out your pattern of business calls or internet use throughout the year.”

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5. Occupancy expenses are usually worked out from the percentage of the floor area of your home that is a place of business.

   ›What the ATO says

   “You would usually calculate occupancy expenses based on the percentage of the floor area of your home that is a place of business”

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How Bilbx applies it

• Tax Lab, part of Bilbx Premium, applies a category's business-use share for the tax years its record covers: 12-week logbook, for 5 years; 4-week diary, for its own year; floor area, until you change it.
• When a record no longer covers the year, Settings asks for a new one.

Worked examples

Bilbx's own tests run these exact cases against the website and the app.