Operating through a company or trust comes with real advantages. It also comes with obligations that sole traders don't have to think about, and ignoring them gets expensive quickly.
For companies, the big one is the company tax return, due by the end of February if you're lodging through a tax agent. Miss it and you'll get a failure to lodge penalty that accrues over time. Companies also need to manage Division 7A carefully. Any money taken out of the company by a director or shareholder that isn't classified correctly can be treated as an unfranked dividend, which creates a tax bill you weren't expecting.
For trusts, the critical deadline is the trustee resolution. A discretionary trust needs a valid resolution in place by June 30 each year that determines how income will be distributed to beneficiaries. Miss that date and the ATO's default position applies, which usually means the highest marginal rate. There are no extensions. It has to be done before midnight on June 30.
Both structures also require annual financial statements, and if you have employees, payroll tax and superannuation obligations don't disappear because you're operating through an entity.
The compliance burden is manageable but it needs to be calendared. The deadlines are fixed and the penalties for missing them are real. If you're not sure what your obligations are under your current structure, now is a better time to find out than when you're already late.