You do not need to report this interest income to HMRC based on the £500 dividend threshold you cited. That rule applies specifically to share dividend income, not savings interest [1][2]. Your £585.61 is classified as interest from an offshore UK account, which is a different category of income entirely.

For non-UK residents, UK-source savings interest and dividends are generally treated as "disregarded income" under HMRC rules [2]. This means your UK tax liability on the interest is typically limited or eliminated, particularly if no tax was withheld at source. Since you have never been a UK tax resident, the standard UK resident thresholds—such as the Personal Savings Allowance of £1,000 for basic rate taxpayers—do not apply to you in the same way [2].

However, you should verify the exact nature of the payment. If the "offshore UK account" is actually a distribution from a UK company shareholding or close company, different rules may apply, particularly given the new temporary non-residence rules effective from 6 April 2026 [3]. Additionally, whether you must register with HMRC can depend on whether tax was withheld at source and whether any treaty relief applies [2].

Critically, while you likely owe no UK tax and have no reporting obligation to HMRC, you should check your own country of residence's tax requirements. Most countries require their residents to report worldwide income, including interest earned in foreign or offshore accounts. Your compliance obligation to HMRC is likely minimal, but your local tax authority may have different rules.