The deductible portion refers to the percentage of home costs that can be claimed as business expenses in New Zealand. This includes a portion of rent, mortgage interest, utilities, and other home-related costs. The deductible portion is typically calculated based on the area of the home used for business or the time spent working in that space. Understanding and correctly applying the deductible portion is essential for accurately claiming home office deductions and complying with New Zealand tax laws. It ensures a fair and equitable allocation of costs between personal and business use, reflecting actual usage.