Do I need to attach my receipts to the tax return?

Short answer. No.

You don't send any documents or paperwork to HMRC, all you need to do is submit your tax return showing the figures from the records that you have kept.

But you must retain all the documents that evidence the figures you put on your tax return so that HMRC can look at them if they wish to. They will ask you for this information if needed. You need to keep all your business records and documents for 6 years from the tax return deadline of 31st January each year.