"Variation" of a financial order can be of two forms.
First, there may be variation of the amount of maintenance, also known as alimony, or of child support (if previously in a court order). As financial and other circumstances change from year to year including the resources of the paying party and the needs of the recipient (taking account of attempts to obtain employment and/or to become self-sufficient), annual or other reviews of the account of maintenance may be appropriate. It can sometimes be wise to include an automatic increase by reference to retail price indexation. If maintenance was for a fixed term of years, it may sometimes be necessary to vary the length. Applications to vary maintenance are relatively common and require disclosure by both involved. In most instances it can be resolved by negotiation and professional assistance.
Secondly and very different, there may be exceptional circumstances in which the overall terms of a final financial order should be varied. It may be due to a dramatic and/or unexpected change of circumstances soon after the order was made. These variations are unusual and only rarely successful. The law and procedure is complex and legal advice should be taken.