You’ll need to open a separate bank account to operate your business from.  This will need to be an account that is used solely for business.  Keep it separate from your personal accounts so that all your business income and expenses go in and out of it. If you need funds for your personal expenses, transfer the funds into your personal account and pay them from there, rather than using it to pay your personal bills.  This keeps it clean and tidy and draws a line in the sand between personal and business.

You will need to keep all your receipts and invoices for expenses.  To keep paper copies of receipts and invoices, IRD requirement is that you keep them for seven years. If the thought of keeping stacks of paperwork for seven years has you cringing at the thought of where you are going to store all the paperwork, you can use an app like Hubdoc that you can load on your phone to take photos of your receipts or forward emailed copies of your receipts to and then it sends copies of them through to Xero so that they get stored electronically in Xero next to the transaction in there. If you use a system like this, you can ditch all those paper copies and rely on the electronic copies.