You may reapply at any time after your refusal. However, since ties are considered to be things that cannot generally change overnight, allowing a reasonable period between your previous refusal and your next application may better strengthen your case. What is reasonable is relative is relative and may depend on the circumstances of each case. However, a period of between 6 months and a year may be considered as reasonable. In considering whether to reapply, you may consider whether you explained your situation accurately at the interview or whether the CO overlooked something in your application. You may also consider whether you have any additional information you can present to establish your ties.