Provide Receipt or Not

Do I by law have to provide a receipt for payment of a service business (hairdressing or house cleaning for example) if my annual income is under $30,000 and I do not collect tax?

I understand that it is the law to give a receipt when asked by the customer but wondering if I would need to always write one out anyway for my records.

Sorry, I don't know whether it's law ... I do know some customers don't want invoices/receipts ... however, it is really hard to keep an accurate set of books and stay on the good side of CRA without having a way for YOU to track your sales.

By not creating an invoice or receipt for each sale you risk understating your sales. Under reporting sales is called skimming. You can read more about skimming and its consequences here.

CRA frowns upon this type of activity ... in fact it's illegal.

In my article on good bookkeeping practices (follow the link above), there is a side bar that explains how to record your "cash under the table" transactions.