Paying The Tax For The £500 Self Isolation Payment

HMRC are sending out the tax codes for the new financial year which begins on April 6 and quite a few people are looking at it and noticing that they have an adjustment in their tax code due to an underpayment of £100 tax in this current tax year.
After a bit of asking around it transpired that all of these people have been in receipt of the £500 Self-Isolation payment from the Government, a payment for anyone who tests positive for Coronavirus and is asked to self-isolate but are unable to work from home who will suffer financially by self-isolating.
There are no figures available for the exact number of people who were in receipt of the payment but 6.4 million people in England were told to self-isolate by contact tracers which gives us a ballpark figure of how many people were eligible for the payment.
HMRC are informed by the local Council of who received this payment and the Tax Man treats it as Additional Earnings and as it is not taxed, lump it in with your other earnings for the year and if you have earned above the £12,500 limit, 20% tax is due on the £500 which is where the £100 underpayment comes in.
HMRC have confirmed that if if the underpayment cannot be collected through your Tax Code for any reason, you can make regular payments through your Personal Tax Account until the amount is paid off but maybe the Government should have made it clear that the £500 was taxable before they began pushing people to apply for it.