National Insurance number suffix chane?

[Buteo]

Just been sorting out DH's tax return (nothing like leaving it to the last minute ) and he seems to have two versions of his NI number - one with an A suffix which is on his payslips and last year's tax return done by the accountant, and one with a B suffix which was automatically entered on the on-line self assessment form.

DH tells me that it was originally with a B suffix and it changed to an A suffix for some unknown reason.

I know that the first set of letters and the numbers are unique, so having different suffix letters shouldn't confuse his records with anyone else's, but will his records tie up OK if there are two versions of his number being used that vary only by suffix?

The Suffix
The suffix dates back to when contributions were recorded on cards which were returned annually, staggered throughout the tax year. “A” meant the card was to be returned in March; “B” in June; “C” in September; and “D” in December. Although contribution cards are no longer used, the suffix has remained an integral part of the NINO.