If your spouse does not work elsewhere and they actually do some tasks within the business then you could consider paying them a salary.
Your spouse has to actually do the work and be paid a fair rate for the actual hours they do for the company. If queried, HMRC would expect evidence of work activity such as emails, spreadsheets etc to support the wages paid.
From April 2016 the Employment Allowance (up to £3,000 a year off your National Insurance bill if you’re an employer) no longer applies to single director companies.
Given this, in all likelihood HMRC will be keener to examine salaries paid to spouses if they think this is really just tax avoidance rather than genuine payment for work done.
Make them a Director
A common solution to this is for your spouse to become a Director of your company as they can receive payment just for holding the office.
However it is very important to realise being a director has legal responsibilities; hence the payment for being an Office Holder of the company.
While this may not usually be very relevant in a typical small company, that doesn’t mean it would never be relevant if something unexpected went wrong.
Finally worthy of mention is the Marriage Allowance. This allows you to transfer £1,100 of your Personal Allowance to your husband, wife or civil partner – if they earn more than you.
There are rules to follow for the marriage allowance – you can read more at https://www.gov.uk/marriage-allowance/how-it-works