What happens after submitting SA303?

I've just submitted my SA and realised my payments on account for next year will be too much as I expect to take a smaller dividend from my company. I've calculated my expected figures but I'm not an accountant. If I submit the form, will HMRC contact me and validate my calculations? I'm concerned if I underpay and get charged interest... Many thanks

Hi,

You are able to amend a tax return after you have filed it - you can find out more information on how to do this here:

Self Assessment tax returns

Thank you.