When life is going 100 miles an hour, as an owner established/growing business, you should keep your finger on the pulse.
All you need to make sure
On a monthly basis, you run your payroll and send necessary reports to to HMRC and make the require payment.
You will need to prepare your VAT return and submit it to HMRC.
Ensure that you submit the confirmation statement to the companies house.
Prepare annual accounts and corporation tax return and file them with the companies house and HMRC.
Finally, prepare your own Self Assessment Tax return and send it to HMRC.
This is a list of most common tasks for businesses in general. However, special rules might be applicable for your business. For example, if you sale good/services to Europe, in addition to VAT returns, you will have to send EC sales lists.