UK immigration rules set out the requirements for family visas and one of them is meeting the financial requirement. An amount based on the cash savings above £16,000 held by the applicant, their partner, or both jointly or a child dependant relative who is over 18 for at least the 6 months prior to the date of application and under their control can count towards the financial requirement under Category D. (£16,000 is the level of savings at which a person generally ceases to be eligible for income-related benefits).
Category D: Cash savings can be combined with income from Category A: salaried and non-salaried employment, part (1) of Category B: salaried and non-salaried employment, Category C: non-employment income and Category E: pension in order to meet the financial requirement.

Cash savings cannot be combined with some income categories
Category D: Cash savings cannot be combined with self-employment income, or with income from employment as a director or employee of a specified limited company in the UK, under either Category F or Category G: see Category F: last full financial year section of this guidance. Category D: Cash savings also cannot be combined with part (2) of Category B: salaried and non-salaried employment: see Category B: less than 6 months with current employer or variable income – person residing in the UK section of this guidance. The rules and requirements are set out in UK immigration rules.
Combining cash savings with employment income
For those in paid employment at the date of application, current cash savings may be used to make up any deficit in the current gross annual income of that employment (and / or in the confirmed employment in the UK to which they are returning, in the case of overseas sponsors), in order to meet the financial requirement.
However, those who have held that employment at the level of income relied upon for less than 6 months at the date of application have in addition to show that they meet the financial requirement over the 12 months prior to the date of application. In doing so, they cannot combine their current cash savings with their past earnings over that earlier period, because this would not be an accurate indicator of the real level of financial resources available to the couple. It could also lead to the same money being counted twice, once as earnings and later as savings. A similar approach is taken towards those in self-employment, or in employment as a director or other employee of a specified limited company, who have to show their past earnings over the previous financial year or years.