It probably has to relate to the business and not be 'domestic services'. Cleaning, childcare etc of one's own home is not tax deductable in the UK.
I think there has to be a demonstrable amount of work done by the partner that benefits the business that is paid in line with what a standard, unrelated employee would earn. So not £12k pa for 2 hours a week for example.
Bit if the partner of a builder or other tradesman did all his quotes, invoicing, making appointments, ordering materials, doing the VAT return, checking bank accounts etc etc, that would probably be OK.
However, if you ran a joint account for household bills and spending this would be money you had access to that wouldn't count as your taxable income, but wouldn't reduce his taxable income either.
However, if you are married and a non tax payer and he is a standard rate tax payer, you can transfer some of your allowance to him, which reduces his tax bill.