Credit is limited to what your suppliers have actually declared.
An invoice from one financial year has to be claimed by a cutoff in the next — broadly the November return of the following year, or the annual return, whichever is earlier.
Some credit is blocked by law regardless of business use — motor vehicles below a seat threshold, food and beverages, club memberships, health insurance except where mandated, works…
If you do not pay a supplier within 180 days of the invoice date, credit already taken must be reversed, with interest.
If you make both taxable and exempt supplies, credit on common inputs has to be apportioned, and the exempt portion reversed.
An invoice raised to your other branch, your personal name, or an old registration does not give you credit — it gives it to whoever is named.
Input credit is where most GST money is lost, and rarely through fraud. Six ordinary errors, what each one costs, and how to catch them monthly instead of at audit.