By my reckoning you will earn ((€14,956.17 @ 5.22%) / 365) * 31) = €66.31 in January. €14,956.17 + €66.31 = €15,022.48 so you will be pushed above the €15K limit when the interest is added which will impact the interest earned until you reduce the deposit balance. Might be safest to keep a maximum of about €14,930 on deposit if you are collecting/transferring interest monthly in order to never breach the limit? That means a maximum of €66.19 interest per month (31 day month) which will being you to €14,996.19. On the other hand perhaps one could keep €14,999.99 on deposit and as soon as interest is paid transfer it out? Maybe you will just get the lower rate on the day that the interest is credited but once you transfer out you will revert to the higher rate? Not sure what the T&Cs say about this but I presume that interest is calculated daily but credited monthly?