Catch up-Contributions

If you had HDHP coverage for the full year, you can make the full catch-up contribution regardless of when your 55th birthday falls during the year. If you did not have HDHP coverage for the full year, you must pro-rate your "catch-up" contribution for the number of full months you were "eligible", i.e., had HDHP coverage.

Now here is where the fun starts

If a couple are both over 55 and each want take advantage of the Catch-up Contributions (are you sitting down?) they each must have an HSA account.
The following is from the U.S Treasury's website:

If both spouses are 55 and older, can both spouses make "catch-up" contributions? Yes, if both spouses are eligible individuals and both spouses have established an HSA in their name. If only one spouse has an HSA in their name, only that spouse can make a "catch-up" contribution.

So what does this mean?

Let's say for example they have a $5000 deductible policy. The most they can put in one account is $5600 and $600 in another or they can split up the $6200 any way they want in 2 HSA accounts.