Hi Its MamaTax Here!
Thanks for asking the question.
Yes you can correct your tax return online or send HM Revenue & Customs (HMRC) the pages of your paper tax return (mark them ‘amendment’). The deadline for this is 12 months after the tax return deadline (eg 31 January).If the period you refer to relates to a period more than 12 months ago then you need to write to HMRC and: confirm the tax year you’re correcting explain why you’ve paid too much tax include proof you’ve paid the tax in that year confirm how you want the refundThe deadline for writing to HMRC is 4 years after the end of the tax year you’re correcting for such corrections. If you have any refunds, HMRC will let you know how much your refund is (including interest). If you owe more tax, HMRC will let you know how much tax you owe (including interest) and when to pay them.You can use this address below to post your documents:HM Revenue & CustomsSelf AssessmentPO Box 4000CardiffCF14 8HR Hope this helps.