The short answer: No, not usually. The CMS calculates from your effective date, which is normally the date you applied. You cannot claim for the years before that. But two things are frequently mistaken for backdating and are both recoverable: maintenance that built up while the CMS was processing your application, and unpaid amounts under an assessment that already existed. The second of those has no time limit at all.

Is child maintenance backdated?

In general, child maintenance through the CMS is not backdated to the date of separation. Payments are calculated from the date the CMS opens a case, meaning the date your application is received and processed.

Backdating and arrears are not the same thing

This single confusion accounts for most of the disappointment people feel on this subject, and most of the false hope.

  • Backdating means creating liability for a period before any arrangement existed. This is what the CMS generally cannot do.
  • Arrears means unpaid amounts under a liability that already existed. There is no time limit on these. A balance from the CSA era in the 1990s is still legally enforceable today.

So if you were assessed at £80 a week in 2012 and the other parent stopped paying in 2014, none of that is lost. If you separated in 2012 and never applied until now, the earlier years generally are. Our guide to CMS arrears time limits covers the second situation in full, and our arrears calculator works out what you are owed.

From what date does the CMS calculate payments?

The CMS starts calculating from the date they receive your application (or the date the case opens if the paying parent applies). You will not usually receive payments for the period before the application was made.

How far back can I claim child maintenance?

You cannot typically claim maintenance for periods before the CMS case was opened. If you separated years ago and have not yet applied to the CMS, you will not receive payments for those years.

Apply early. The sooner you apply to the CMS, the sooner your entitlement starts. Delays in applying mean lost maintenance that you cannot reclaim.

Can CMS payments be backdated due to CMS delays?

If the CMS itself causes significant delays in processing your case, you may be able to request that payments are backdated to your original application date rather than the date the case was formally opened. This is known as an administrative delay and you should raise it directly with the CMS.

What about arrears from a previous arrangement?

If the paying parent has missed payments under an existing CMS or CSA arrangement, those are treated as arrears rather than backdating. The CMS can pursue arrears, and they do not disappear when a child turns 16 or 20.

Private arrangements and backdating

If you had a private arrangement that was not honoured, a court may sometimes award backdated payments as part of a broader financial settlement, particularly if the paying parent was shown to have deliberately avoided paying. This requires court proceedings with a family solicitor.