For a family business it is generally worthwhile paying wages to a spouse of between £111 (£112) (the employee lower earnings limit) and £153 (£155) (the employee threshold) per week.
At this level of earnings no NIC will be due. The employee will accrue entitlement to a state pension and certain other state benefits.
A PAYE scheme would be needed to record the employee's entitlement to benefits and the wages.
For the self-employed there is a requirement to pay a flat rate contribution (Class 2). If your profits are low you can apply for exemption. The limit is £5,885 (£5,965). If contributions have been paid for 2014/15 and it subsequently turns out that earnings are below £5,885 a claim for repayment of contributions can be made. The deadline for this claim is 31 January 2016.
On the other hand as the contributions are only £2.75 (£2.80) a week it may be advisable to pay the contributions in order to maintain a contributions record. The alternative voluntary Class 3 contributions are £13.90 (£14.10) a week!